Comeback concerning civil wrong (6)
I believe the answer is:
retort
'comeback' is the definition.
(I know that comeback can be written as retort)
'concerning civil wrong' is the wordplay.
'concerning' becomes 're' (both can mean on a particular topic).
'civil wrong' becomes 'tort' (synonyms).
're'+'tort'='RETORT'
(Other definitions for retort that I've seen before include "may be found in lab" , "A sharp reply or vessel used in distilling" , "Long-necked glass vessel" , "Rotter (anag.)" , "Respond" .)