Get too big (for) (7)
I believe the answer is:
outgrow
'get too big for' is the definition.
(to outgrow something is to get too big for it)
This is all the clue.
(Other definitions for outgrow that I've seen before include "Get bigger" , "Become too big for" , "excel in development" , "Become too large or too mature for" , "Develop beyond" .)