Girl who is about to have a meal (4)
I believe the answer is:
enid
'girl' is the definition.
(girl's name)
'is about to have a meal' is the wordplay.
'is about' is a reversal indicator.
'to have a meal' becomes 'dine' (I've seen this before).
'dine' reversed gives 'ENID'.
'who' acts as a link.
(Other definitions for enid that I've seen before include "- Blyton, twentith century writer" , "Dine out on this girl's name also" , "- Blyton, children's writer" , "Writer of children's books, d. 1968" , "Miss Blyton" .)