Deny agent is wrong over a point (6)
I believe the answer is:
'deny' is the definition.
(I know this)
'agent is wrong over a point' is the wordplay.
'is wrong' indicates an anagram.
'over' indicates putting letters inside.
'a point' becomes 'e' (compass point).
'agent' anagrammed gives 'ngate'.
'ngate' going around 'e' is 'NEGATE'.
(Other definitions for negate that I've seen before include "Cause to have no effect" , "Make invalid" , "Disprove or nullify" , "Opera by Puccini" , "Cancel; invalidate" .)