Large cask turning the head (3)
I believe the answer is:
tun
'large cask' is the definition.
(type of container for alcohol)
'turning the head' is the wordplay.
'turning' shows that the letters should be reversed in order.
'the head' becomes 'nut' (informal term for somebody's head).
'nut' written backwards gives 'TUN'.
(Other definitions for tun that I've seen before include "Barrel holding many gallons" , "Large cask or barrel" , "butt" , "Nut found in large cask" , "One can hold wine" .)