Head found in barrel rolled back (3)
I believe the answer is:
nut
'head' is the definition.
(informal term for somebody's head)
'barrel rolled back' is the wordplay.
'barrel' becomes 'tun' (tun is a kind of barrel).
'rolled back' says the letters should be written in reverse.
'tun' backwards is 'NUT'.
'found in' is the link.
(Other definitions for nut that I've seen before include "Screwing block" , "Hard-cased fruit" , "piece of coal" , "Hard-headed person" , "organized teachers" .)