Friend embracing sweetheart, sound as a bell (4)
I believe the answer is:
peal
'sound as a bell' is the definition.
(to peal is to ring)
'friend embracing sweetheart' is the wordplay.
'friend' becomes 'pal' (pal is a kind of friend).
'embracing' is an insertion indicator.
'sweetheart' becomes 'e' (the heart/centre of 'sweet').
'pal' enclosing 'e' is 'PEAL'.
(Other definitions for peal that I've seen before include "Sound of bells, thunder" , "Leap about to sound of bells" , "Set of bells for ringing" , "(Bells) ring" , "Carillon" .)