Passage about a former coin (5)
I believe the answer is:
ducat
'coin' is the definition.
(ducat is a kind of coin)
'passage about a former' is the wordplay.
I cannot really see how this works, but
'about' could be 'ca' (abbreviation for circa) and 'ca' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for ducat that I've seen before include "Antique coin" , "Old Italian coin" , "Old European gold or silver coin" , "Ancient coin" , "Former Italian gold coin" .)