Develop flower, having shapeless edges (7)
I believe the answer is:
blossom
'develop' is the definition.
(I know that blossom is a kind of develop)
'flower having shapeless edges' is the wordplay.
'flower' becomes 'bloom' (synonyms).
'having' indicates putting letters inside.
'edges' means to remove the middle letters (I've seen 'edges of' mean this).
'shapeless' with its middle removed is 'ss'.
'bloom' placed around 'ss' is 'BLOSSOM'.
(Other definitions for blossom that I've seen before include "Produce flowers" , "Grow" , "Flowers on, eg, cherry" , "Flowers on a tree/bush" , "attractive growth" .)