Feature of car used in hasty retreat (4)
I believe the answer is:
tyre
'feature of car' is the definition.
'in hasty retreat' is the wordplay.
'in' indicates a hidden word.
'TYRE' is hidden in the letters of 'hasty retreat'.
'used' acts as a link.
(Other definitions for tyre that I've seen before include "Rubber wheel casing" , "Old Phoenician port" , "subject to inflation" , "Pneumatic wheel cover" , "Wheel cover, may be tubeless" .)