Boy about to press for the operator (7)
I believe the answer is:
surgeon
'the operator' is the definition.
(I've seen this before)
'boy about to press for' is the wordplay.
'boy' becomes 'Son' (synonyms).
'about' is an insertion indicator.
'to press for' becomes 'urge' (I've seen this in another clue).
'son' placed around 'urge' is 'SURGEON'.
(Other definitions for surgeon that I've seen before include "Sawbones" , "Medical knife wielder" , "one performing in the theatre" , "Doctor in the navy" , "9 practitioner (through keyhole?)" .)