Grows into suits (7)
I believe the answer is:
becomes
I believe this clue is a double definition.
'grows' is the first definition.
'suits' is the second definition.
('become' can be a synonym of 'suit')
'into' acts as a link.
(Other definitions for becomes that I've seen before include "Changes into" , "Undergoes a change" , "Gets" , "Turns into" , "Suits, befits" .)