Old sixpence (6)
I believe the answer is:
tanner
'old sixpence' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for tanner that I've seen before include "Formerly 6d (sl.)" , "once seeing heads and tails here?" , "Hide worker; old coin" , "One beating" , "Old sixpenny piece" .)