Explosion with sulphur taken to heart (5)
I believe the answer is:
bosom
'to heart' is the definition.
(bosom can figuratively mean the heart)
'explosion with sulphur' is the wordplay.
'explosion' becomes 'boom'.
'with' means one lot of letters goes inside another.
'sulphur' becomes 'S' (synonyms).
'boom' enclosing 's' is 'BOSOM'.
'taken' acts as a link.
(Other definitions for bosom that I've seen before include "5 [BUST]" , "Embrace" , "Chest; very close (friend)" , "A close affectionate and protective acceptance" , "Breast, chest" .)