Injury extremely bizarre admits servant (5,3)
I believe the answer is:
black eye
'injury' is the definition.
(black eye is a kind of injury)
'extremely bizarre admits servant' is the wordplay.
'extremely' suggests removing the centre.
'admits' is an insertion indicator.
'servant' becomes 'lackey' (lackey is a kind of servant**).
'bizarre' with its middle taken out is 'be'.
'be' going around 'lackey' is 'BLACK EYE'.
(Other definitions for black eye that I've seen before include "Outcome of strike" , "Bruise on face" , "Key cable (anag)" , "Facial bruising" , "Result of blow to optic" .)