I'm going round in reverse in car (4)
I believe the answer is:
mini
'car' is the definition.
(Mini Cooper)
'i'm going round in reverse' is the wordplay.
'i'm' becomes 'im' (**).
'going round' is a reversal indicator.
'reverse' says the letters should be written in reverse.
'im' backwards is 'mi'.
'in' reversed gives 'ni'.
'mi'+'ni'='MINI'
'in' is the link.
(Other definitions for mini that I've seen before include "Baby" , "Once fashionable skirt" , "type of garment" , "Cult British car" , "Brief" .)