Plant covering base of wheel in vehicle (6)
I believe the answer is:
sledge
'vehicle' is the definition.
(sledge is a kind of vehicle)
'plant covering base of wheel' is the wordplay.
'plant' becomes 'sedge' (sedge is a plant).
'covering' means one lot of letters goes inside another.
'base of' suggests the final letters.
The final letter of 'wheel' is 'l'.
'sedge' enclosing 'l' is 'SLEDGE'.
'in' acts as a link.
(Other definitions for sledge that I've seen before include "Large heavy hammer" , "one could go downhill fast" , "Try rattling opposing players" , "Make offensive remarks" , "In Canada train" .)