Finery of sporting gear worn by boxer (7)
I believe the answer is:
regalia
'finery' is the definition.
(synonyms)
'sporting gear worn by boxer' is the wordplay.
'sporting' is an anagram indicator.
'worn by' indicates putting letters inside (I've seen this in other clues).
'boxer' becomes 'ali' (Muhammad Ali).
'gear' is an anagram of 'rega'.
'rega' enclosing 'ali' is 'REGALIA'.
'of' acts as a link.
(Other definitions for regalia that I've seen before include "Crown and associated pieces" , "Ceremonial emblems of high office" , "Royal accoutrements" , "Insignia of royalty or office" , "Finery" .)