Colm Collins’ charges are now on eight points and a win over Kildare in Newbridge next Sunday would see them ply their trade in Division 2 next season.
The O’Farrell County were first off the mark when team captain Michael Quinn grabbed a goal on six minutes following a delivery by Barry McKeon.
Clare’s opening score, a point, came courtesy of attacking wing-back Jamie Malone a minute later.
In an evenly fought opening half, the hosts got their only goal after 17 minutes when David Tubridy finished off a move that began with Keelan Sexton and also involved full-forward Pat Burke.
That put them 1-3 to 1-2 in front and from then on they were never lead.
At half-time Longford trailed by 1-7 to 1-6 and just before the break Clare lost corner-back Marty McMahon to a black card.
Clare began the second period in determined mood and kicked seven unanswered points inside the opening ten minutes, killing off the Longford challenge.
Jamie Malone on three occasions, Pearse Lillis twice and one each by Sexton and Eoin Cleary lifted the home support in the 1,226 crowd. Longford lost their mojo after half-time and it took them until the 66th minute to record the first score of the half, a close in free by Brian Kavanagh.
At times, during the second-half there was only one team in it. Clare took their scoring chances at will with man-of-the match Malone hitting the target on five occasions from wing-back.
The biggest cheer of the day came for the introduction of Podge Collins in the 55th minute as the Cratloe man and dual inter-county star returned after a long injury lay-off.
D Tubridy (1-5, 3 frees; J Malone (0-5); E Cleary (0-4); P Lillis, K Sexton (0-2 each); C O’Connor, S McGrath (0-1 each).
B Kavanagh (0-6); M Quinn, B Farrell, D Masterson, J McGivney (0-1 each).
J Hayes, S Malone, K Harnett, M McMahon, J Malone, G Kelly, C O’Dea, G Brennan (Capt.), C O’Connor, S Collins, E Cleary, P Lillis, K Sexton, P Burke, D Tubridy.
S McGrath for S Collins (44), P Collins for Burke (55), E Coughlan for Sexton (55), S Haugh for S Malone (58), J O’Dea for Kelly (61).
P Collum, D Masterson, B Gilleran, C. P. Smyth, D McElligot, D Brady, D Reynolds, J McGivney, M Quinn (Capt.), R Smyth, D Gallagher, B McKeon, M Hughes, B Kavanagh, B Farrell.
R Connor for McKeon, (h/t), S Kenny for Gallagher (48), P McKeon for Hughes (50), L Moran for R Smyth (51), C Farrelly for Reynolds (61), S Doyle for Farrell (69).
L Devenney (Mayo)