Put out again about subject under discussion (7)
I believe the answer is:
reissue
'put out again' is the definition.
(to publish or put out again)
'about subject under discussion' is the wordplay.
I cannot really see how this works, but
'about' could be 're' (regarding) and 're' is found in the answer.
'subject' could be 'issue' (synonyms) and 'issue' is present in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for reissue that I've seen before include "Circulate a second time" , "Do 11 Down again" , "Republish" , "New book version" , "A second impression, perhaps" .)