Strange argot no longer in use (5)
I believe the answer is:
groat
'no longer in use' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'strange argot' is the wordplay.
'strange' indicates an anagram.
'argot' anagrammed gives 'GROAT'.
Can you help me to learn more?
(Other definitions for groat that I've seen before include "Old coin worth four pence" , "Medieval coin" , "Old four-pence coin" , "Old English coin worth four pennies" , "Old English silver coin" .)