Grew to be or developed into something (6)
I believe the answer is:
became
I believe this is a double definition.
'grew to be' is the first definition.
(I've seen this in another clue)
'developed into something' is the second definition.
(I've seen this before)
(Other definitions for became that I've seen before include "Got to be" , "Underwent a change" , "Turned into" , "Developed into something" , "Changed into" .)