Something said about former currency (6)
I believe the answer is:
remark
'something said' is the definition.
(a comment or utterance)
'about former currency' is the wordplay.
'about' becomes 're' ('re' means regarding or about).
'former currency' becomes 'mark' (I have seen 'old currency' mean 'mark' so perhaps 'currency' could also mean 'mark'. I am not sure about the 'former' bit.).
're'+'mark'='REMARK'
Can you help me to learn more?
(Other definitions for remark that I've seen before include "Notice or comment on" , "Observation - notice" , "Say as a comment" , "Comment, observation" , "Comment or mention" .)