Bar getting hold of cask stout (6)
I believe the answer is:
rotund
'stout' is the definition.
(I've seen this before)
'bar getting hold of cask' is the wordplay.
'bar' becomes 'rod' (both can mean a pole or stick).
'getting hold of' indicates putting letters inside.
'cask' becomes 'tun' (tun is a kind of cask).
'rod' enclosing 'tun' is 'ROTUND'.
(Other definitions for rotund that I've seen before include "stout" , "Spherical" , "Portly" , "Chubby" , "'Corpulent, round (6)'" .)