Growing to be attractive (8)
I believe the answer is:
becoming
This clue is a double definition.
'growing' is the first definition.
(I've seen this before)
'attractive' is the second definition.
(I've seen this before)
'to be' is the link.
(Other definitions for becoming that I've seen before include "Appropriate" , "fetching" , "Turning into - lovely" , "attractive" , "Turning into; suiting" .)