Vehicle with caterpillar treads (7)
I believe the answer is:
crawler
'vehicle with caterpillar treads' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for crawler that I've seen before include "Sycophant" , "Obsequious person" , "Minion" , "Figure that's greasy" , "Slow driver" .)