Change into suit (6)
I believe the answer is:
become
I believe this clue is a double definition.
'change into' is the first definition.
(I've seen this in another clue)
'suit' is the second definition.
(becoming can mean fitting or suitable)
(Other definitions for become that I've seen before include "Flatter" , "Develop into something" , "Evolve into; suit" , "Change into - suit" , "Suit, befit" .)