Tot's vocal power (5)
I believe the answer is:
might
'power' is the definition.
(I know that power can be written as might)
'tot's vocal' is the wordplay.
'tot' becomes 'mite' (both can mean a young child).
'vocal' indicates a 'sounds like' (homophone) clue.
'mite' is a homophone of 'MIGHT'.
(Other definitions for might that I've seen before include "- - and main" , "Strength - could possibly" , "Great power/strength" , "Great power, strength" , "Powerfulness" .)