Becoming match fit (8)
I believe the answer is:
suitable
'becoming' is the definition.
(thesaurus)
'match fit' is the wordplay.
'match' becomes 'suit' (suiting is a kind of matching**).
'fit' becomes 'able' ('able' can be similar in meaning to 'fit').
'suit'+'able'='SUITABLE'
(Other definitions for suitable that I've seen before include "In keeping" , "Right or appropriate" , "Appropriate, befitting" , "qualified" , "Fitting, apt" .)