Goals by Mark Lamont and Ross Cunningham gave them a 2-0 success which lifted them above their opponents in the battle to avoid the relegation play-offs.
The result also confirmed Forfar go down automatically.
Now victory in their rearranged match against East Fife next Thursday will guarantee League 1 football for Danny Lennon’s side next season, even if Dumbarton win their final match against Peterhead on Tuesday.
Dumbarton should have been ahead inside two minutes, Robin Omar hitting the post after an error in defence by David Goodwillie allowed him in on goal.
The visitors threatened again on eight minutes as Adam Frizzell set up Robert Jones whose fierce left-foot strike was safely gathered by David Wilson.
The Bully Wee then had a great chance to take the lead when Ross Cunningham's ball into the danger area met by Martin McNiff sliding in six yards out, but he couldn't keep shot down and it flew over the bar.
Given what was at stake it was an understandably nervy encounter.
But the home side weren't far away from the opener on 26 minutes, Goodwillie sending a header just over from a hanging Jamie Bain cross.
The goal was only delayed a few minutes though. Just after the half-hour Mark Lamont took possession just outside the box and lashed a sizzling strike beyong the keeper Sam Ramsbottom’s despairing dive
The sides were still separated by that strike at the break.
As Dumbarton pushed for an equaliser in the second half Ross Forbes's set piece deliveries were a source of danger for Clyde.
But at the other end a brilliant driving run into the box by Ross Cunningham, almost fashioned an opening but Clyde couldn't take advantage of his ball across and the Sons survived the scare.
However Clyde were defending deeper and deeper as the half progressed and Wilson did well to come off his line and save at the feet of PJ Crossan.
The young keeper pulled off an even better save to keep out a Wallace header.
And its importance was rubber stamped just a couple of minutes later when Clyde doubled their advantage..
Fine hold-up play by Goodwillie created the opportunity for Ally Love to play in Cunningham and he coolly slid the ball low past the advancing keeper.
That gave Clyde the cushion they needed for the closing 15 minutes.