Sycophant in slow-moving vehicle (7)
I believe the answer is:
crawler
I believe this clue is a double definition.
'sycophant' is the first definition.
(synonyms)
'slow-moving vehicle' is the second definition.
(a construction vehicle which moves slowly)
'in' is the link.
(Other definitions for crawler that I've seen before include "Minion" , "Toady" , "Figure that's greasy" , "Sycophant" , "heavy slow-moving vehicle" .)