Rear or reverse (4)
I believe the answer is:
back
This clue is a double definition.
'rear' is the first definition.
(synonyms)
'reverse' is the second definition.
(I've seen this before)
(Other definitions for back that I've seen before include "Support (from behind?)" , "Golf holes 10-18" , "ago" , "Stern" , "Series of popular time-travel movies" .)