Head pupil at Eton, say, may get a pantomime role (9,3)
I believe the answer is:
principal boy
'a pantomime role' is the definition.
(leading role in a pantomime)
'head pupil at eton say' is the wordplay.
'head' becomes 'principal' (principal can mean a head teacher).
'pupil at eton say' becomes 'boy' (Eton is a boys' school).
'principal'+'boy'='PRINCIPAL BOY'
'may get' is the link.
(Other definitions for principal boy that I've seen before include "Male pantomime hero played by actress" , "cross-dressing player" , "part in panto" , "Pantomime lead" .)