Boy of resonance (3)
I believe the answer is:
son
'boy' is the definition.
(male child)
'of resonance' is the wordplay.
'of' indicates the answer is hidden within the clue.
'SON' can be found hidden inside 'resonance'.
(Other definitions for son that I've seen before include "Young boy" , "Male child" , "Heir" , "A relative" , "Male offspring" .)