Clothes Martin changed about the end of June (7)
I believe the answer is:
raiment
'clothes' is the definition.
(raiment is a kind of clothes)
'martin changed about the end of june' is the wordplay.
'changed' indicates anagramming the letters.
'about' is an insertion indicator.
'the end of' says to take the final letters.
The final letter of 'june' is 'e'.
'martin' with letters rearranged gives 'raimnt'.
'raimnt' placed around 'e' is 'RAIMENT'.
(Other definitions for raiment that I've seen before include "Am inert (anag) - clothing" , "Old word for fine clothing" , "Attire" , "Something put on" , "Clothing (archaic)" .)