Concerned with wrong but sharp answer (6)
I believe the answer is:
retort
'sharp answer' is the definition.
(I've seen this before)
'concerned with wrong' is the wordplay.
'concerned with' becomes 're' (re can mean regarding, concerning).
'wrong' becomes 'tort' (a civil wrong in law).
're'+'tort'='RETORT'
'but' is the link.
(Other definitions for retort that I've seen before include "Lab. vessel; quip" , "Quick rejoinder" , "Reply sharply, perhaps angrily" , "Respond" , "Sharp riposte" .)