Opposite concerning poetry (7)
I believe the answer is:
reverse
'opposite' is the definition.
(I've seen this before)
'concerning poetry' is the wordplay.
'concerning' becomes 're'.
'poetry' becomes 'verse' ('verse' can be a synonym of 'poetry').
're'+'verse'='REVERSE'
(Other definitions for reverse that I've seen before include "Rescind (decision)" , "Travel backwards" , "Back (of a coin or medal)" , "Setback; go back" , "Severer (anag.)" .)