Having fallen behind to an early try from a blindside break, Oscar James levelled things up for the visitors when he latched on to a neat offload from Will Trollope to score next to the posts.
But Cullompton hit back soon after and another couple of scores before the break gave them a comfortable lead at the break.
The pressure continued after half-time, but Clevedon stayed in touch with a score from Harley Foley.
But the hosts soon put the game to bed when, following a number of missed tackles, they scored under the posts.
Oli Jones powered over for a late consolation for Clevedon, but Cullompton went through the 50 point barrier to condemn Clevedon to another heavy defeat on the road.