Four old pence (5)
I believe the answer is:
groat
This clue might be a double definition.
'four old' is the first definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'pence' is the second definition.
(thesaurus)
Can you help me to learn more?
(Other definitions for groat that I've seen before include "Old fourpenny coin" , "Medieval coin" , "Old four-pence coin" , "Old coin worth four pence" , "Old English coin worth four pennies" .)