For Louis I, reversing sports car (4)
I believe the answer is:
jeep
'car' is the definition.
(jeep is a kind of car)
'for louis i reversing sports' is the wordplay.
'for louis i' becomes 'je' ('I' in French - Louis is a common French name).
'reversing' says the letters should be written in reverse.
'sports' becomes 'pe' (Physical Education).
'pe' written backwards gives 'ep'.
'je'+'ep'='JEEP'
(Other definitions for jeep that I've seen before include "Truck" , "Sturdy vehicle" , "Four-wheel-drive general purpose vehicle" , "US army car" , "4WD vehicle" .)