Sadly rejected, daughter leaves (5)
I believe the answer is:
salad
'leaves' is the definition.
(salad leaves)
'sadly rejected daughter' is the wordplay.
'sadly' becomes 'alas' ('alas' is used to express regret).
'rejected' shows that the letters should be reversed in order.
'daughter' becomes 'd' (genealogical abbreviation).
'alas' back-to-front is 'sala'.
'sala'+'d'='SALAD'
(Other definitions for salad that I've seen before include "Mainly raw cold dish" , "healthy food" , "Counter serving cold vegetable dishes" , "one gets dressed" , "A dish of lettuce and vegetables" .)