Go off in pursuit of normal copy (6)
I believe the answer is:
'copy' is the definition.
(I've seen this in another clue)
'go off in pursuit of normal' is the wordplay.
'go off' becomes 'rot' (as in food going off).
'in pursuit of' is a charade indicator (letters next to each other) (some letters chase after others).
'normal' becomes 'par' (I've seen this in another clue).
'rot' put after 'par' is 'PARROT'.
(Other definitions for parrot that I've seen before include "18's [BIRD]" , "Sick as a -" , "Amazon" , "One repeating" , "Recite" .)