Linnets striker Darran Hay notched his first goal on home soil to maintain Lynn's slim play-off hopes at The Walks.
Hay hammered home his second goal in three games to keep Lynn in touch with the leading pack at the top of the Premier Division standings.
Lynn find themselves 11th with 11 games to go, with several of these against sides also chasing a place in the play-offs.
Linnets manager Tommy Taylor still hasn't given up on the play-offs, but admitted the task ahead will be tough.
An honest Taylor said: "It's simple, if we're going to make the play-offs we have to win nearly every one of our games.
"I have the team here which can do it, but it's all down to having a little bit of luck in front of goal, while making sure that we're nice and solid at the back.
"We played very well in the first half today, but we found it difficult in the second half with a swirling wind, but still tried to pass the ball which pleased me.
"We're getting into scoring positions, but we need to find the back of the net more regularly."
Taylor also revealed the reason for playing Danny Bloomfield in a more deeper role behind Hay.
"If you can conquer the midfield than you can conquer this division," commented Taylor. "Playing Danny a bit deeper and leaving one player up front has helped us just by having that extra person helping the midfield."
Lynn lost the influential Simon Clark early on after the defender's hamstring tightened up, but it didn't stop the flow of the match as Lynn surged forward in hunt of an early goal.
The opening seconds saw a fluent move end with Bloomfield's shot being deflected for a corner.
Six minutes later, Hay's flick-on found Defty who placed his effort wide.
Midway through the half substitute Robbie Harris and Bloomfield nearly created an opening for Defty before the ball was scrambled clear.
Gloucester's best chance of the whole game fell to Jimmy Cox in the 25th minute, but the Tigers were foiled by an acrobatic save from Steve Wilson before the ball trickled wide of his left post.
The decisive goal came 13 minutes before the break when Mark Angel's free-kick was headed into the path of Hay by Daniel Hammond for the striker to volley home clinically.
Two minutes later, another quality delivery from Angel was headed over the woodwork by Defty.
A hard-working Gloucester outfit threatened again soon after, but once again Wilson was up to the task when he saved well from point-blank range to deny Neil Mustoe.
Lynn responded with Hammond nodding Angel's centre wide before Hay bravely chipped Matt Bath in the Gloucester goal only to see his effort drop wide of the target.
The Walks outfit applied more pressure on the Gloucester defence after the restart with Angel and Bloomfield both going close to extending the lead.
Angel was guilty of spurning one of the chances of the season, blazing over from six yards out when some fine inter-play saw Harris' cross turned on by Sam McMahon and dummied by Hay.
Lynn continued to hold the upper hand despite not being at their best with McMahon's drive being turned wide and Harris' cross being dug out from beneath his own bar by Bath.
Gloucester's only chance of the second period came midway through the half when the impressive Lee Smith drove wide after finding space inside the Lynn box.
Lynn: Wilson, Jones, Setchell, McMahon, Hammond, Clark (Harris 17 - Quistin 78), Camm, Defty, Hay (Bacon 75), Bloomfield, Angel.
Gloucester City: M. Bath, L. Smith, K. Knight (A. Harris 77), M. Thompson, L. Tomkins, C. Thompson, N. Mustoe, J. Cox, D. Addis, T. Webb, D. Wilkinson (J. Reid 67). Not used: C. Burns.
Referee: J. Hopkins (Wickford, Essex). Attendance: 776.