Child's voice heard (4)
I believe the answer is:
heir
'child's' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'voice heard' is the wordplay.
'voice' becomes 'air' (both can mean to express something).
'heard' indicates a 'sounds like' (homophone) clue.
'air' is a homophone of 'HEIR'.
Can you help me to learn more?
(Other definitions for heir that I've seen before include "One likely to succeed" , "One set to inherit" , "one's to inherit throne!" , "One expected to succeed?" , "The first boy maybe" .)