Child in frivolous programme (5)
I believe the answer is:
sprog
'child' is the definition.
(informal term for a child)
'in frivolous programme' is the wordplay.
'in' indicates a hidden word.
'SPROG' can be found hidden inside 'frivolous programme'.
(Other definitions for sprog that I've seen before include "Infant" , "Child, colloquially" , "little one" , "Child; recruit (mil. slang)" , "Baby (slang)" .)