Old four-pence coin (5)
I believe the answer is:
groat
'old four-pence coin' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for groat that I've seen before include "Old coin worth four pence" , "Old fourpenny coin" , "Old English coin worth four pennies" , "Medieval coin" , "Fourpenny piece" .)