The 29-year old Australian left-back joined the Terriers in January and has since racked up 10 appearances for the English League One side.
It has been non-stop since Heffernan arrived in West Yorkshire and Clark was fully aware of the progress that his new player had made.
"It's been pretty full-on for Dean since he arrived here," Clark told the Huddersfield Examiner.
"But he's settled into the town and the club and I think he's enjoying himself, which is important."
Heffernan originally signed with Huddersfield for the rest of the season before joining new A-League club Melbourne Heart but if he keeps his performances at the level they are already at, he may find himself with a contract extension in England.