Boy and girl about to (5)
I believe the answer is:
anton
'boy' is the definition.
(I've seen this before)
'girl about to' is the wordplay.
'girl' becomes 'ann' (**).
'about' is an insertion indicator.
'ann' enclosing 'to' is 'ANTON'.
'and' is the link.
(Other definitions for anton that I've seen before include "..... Chekov" , "man" , "Chekhov maybe" , "-- Chekhov, Russian dramatist" , "-- Bruckner, composer" .)