Emphasise where one fights in boxing match (5,3)
I believe the answer is:
bring out
'emphasise' is the definition.
(synonyms)
'where one fights in boxing match' is the wordplay.
'where one fights' becomes 'ring' (as in a boxing ring).
'in' means one lot of letters goes inside another.
'boxing match' becomes 'bout' (I've seen this before).
'ring' inserted within 'bout' is 'BRING OUT'.
(Other definitions for bring out that I've seen before include "Emphasize (a feature)" , "Elicit" , "Issue" , "Unveil" , "Publish" .)