Song that guy heard (4)
I believe the answer is:
hymn
'song' is the definition.
(religious song)
'guy heard' is the wordplay.
'guy' becomes 'him' (I've seen this in another clue).
'heard' shows a homophone (sound like).
'him' is a homophone of 'HYMN'.
'that' acts as a link.
(Other definitions for hymn that I've seen before include "Anthem" , "One sung in church" , "Sacred song of praise" , "Orison" , "Song sung in church" .)