Flower girl goes off with a mod (8)
I believe the answer is:
marigold
'flower' is the definition.
(marigold is a kind of flower)
'girl goes off with a mod' is the wordplay.
'goes off with' indicates anagramming the letters.
'a'+'mod'='amod'
'girl' anagrammed with 'amod' can make 'MARIGOLD'.
(Other definitions for marigold that I've seen before include "Orange daisy" , "Bright orange-yellow garden flower" , "Flower - grim load (anag)" , "floral item" , "Yellow or orange flower" .)