They go on wheels, but there's no progress (6)
I believe the answer is:
clamps
'they' is the definition.
Both the answer and definition are plural nouns.
Perhaps you can see an association between them that I don't see?
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for clamps that I've seen before include "Grips" , "fasteners" , "Device to hold things, car wheels say" , "Devices to hold things, car wheels say" , "Holds tightly with device - illegally parked cars? (6)" .)