Fourpenceworth of history (5)
I believe the answer is:
groat
'history' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
'fourpenceworth of' is the wordplay.
I cannot really see how this works, but
'of' could be 'o' and 'o' is found in the answer.
The remaining letters 'grat' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for groat that I've seen before include "Old coin worth four pence" , "Old English silver coin" , "Old fourpenny coin" , "Old English coin worth four pennies" , "Medieval coin" .)