Enemy takes measure of the rim (6)
I believe the answer is:
felloe
'the rim' is the definition.
(felloe is a kind of rim)
'enemy takes measure' is the wordplay.
'enemy' becomes 'foe' (I've seen this before).
'takes' is an insertion indicator.
'measure' becomes 'ell' (I've seen this before).
'foe' going around 'ell' is 'FELLOE'.
'of' acts as a link.
(Other definitions for felloe that I've seen before include "Part of wheel" , "Rim of wooden wheel with spokes attached" , "Part of revolver" , "circular rim" , "edge of revolutionary circle?" .)