Opposite of "inner" (5)
I believe the answer is:
outer
'opposite of inner' is the definition.
('outer' is the opposite to 'inner')
This is all the clue.
(Other definitions for outer that I've seen before include "Ring furthest from the bullseye" , "On the periphery" , "Route (anag.)" , "Poor shot" , "Ring for double scores on a dartboard" .)