The Clydebank man, who beat Craig Lee in a play-off to land his victory last September, took up where he left off on that occasion by carding a bogey-free five-under-par 65.
The effort, which contained birdies at the first, fifth, 10th, 12th and 14th, earned Maclean a one-shot cushion over Kieran Cantley and Paul O’Hara, with Jack McDonald and Robbie Morrison two shots further back in joint-fourth.
“I clearly have good vibes here from my win last year,” said Maclean, who opened with a 66 on that occasion before adding a 69. “I played really nice today. I was out of position a couple of times, but, other than that, it was pretty stress-free.
“The greens are very good and I rolled it great today without holing anything outrageously long.”
The 2017 Irish Open Stroke Play Championship runner-up finished 12th in the season-opening Montrose Links Masters before tying for 26th in last week’s Barassie Links Masters.
“I feel like I have been playing nicely for the last few weeks without really much to show for it, so it is nice to get a low one under my belt,” he added.
Cantley, who turned pro after winning the Pro Golf Tour at the end of 2019, signed for six birdies and was on course to share the lead before dropping a shot at the par-4 16th.
O’Hara, fresh from his win in a 36-holer on the Tartan Tour last week, also had six birdies, including four going out.
Paul Lawrie, the tour founder, sits in a tie for sixth after opening with a 69 alongside amateur duo Gregor Graham (72) and Connor Wilson (74).
Lawrie had set up that group in his new role for Scottish Golf mentoring the country’s brightest young talents.
Sam Locke and Gavin Hay, the winners at Montrose and Barassie respectively, both carded 71s to sit just behind Neil Fenwick, last year’s No 1 on the circuit for home-based players.