Girl and boy return clasping new spring flower (9)
I believe the answer is:
celandine
'spring flower' is the definition.
(plant that grows in spring)
'girl and boy return clasping new' is the wordplay.
I cannot really understand how this works, but
'girl' could be 'andi' and 'andi' is found in the answer.
'and' could be 'n' (common abbreviation for 'and') and 'n' is found in the answer.
This explanation may well be incorrect...
(Other definitions for celandine that I've seen before include "Plant of buttercup family" , "... one blooming" , "Flowering plant - decennial (anag)" , "Land niece with the swallowwort." .)