Power of small child in audition (5)
I believe the answer is:
might
'power' is the definition.
(I know that power can be written as might)
'small child in audition' is the wordplay.
'small child' becomes 'mite' (informal term).
'in audition' shows a homophone (sound like) (audition can mean hearing).
'mite' sounds like 'MIGHT'.
'of' is the link.
(Other definitions for might that I've seen before include "Strength - could possibly" , "Physical strength of old" , "What functions as an auxiliary" , "Capability" , "- - and main" .)