Subcompact (4)
I believe the answer is:
mini
'subcompact' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for mini that I've seen before include "Car designed by Issigonis" , "Iconic economy car (introduced in 1959)" , "(Car etc) of small size" , "Cult British car" , "Short skirt - small car" .)