Go off reeling after knock from Hawk or Eagle (6)
I believe the answer is:
raptor
'hawk or eagle' is the definition.
(I've seen this in another clue)
'go off reeling after knock' is the wordplay.
'go off' becomes 'rot' (as in food going off).
'reeling' becomes 'par' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'after' says to put letters next to each other.
'knock' says the letters should be written backwards (I've seen 'knocking' mean this).
'rot'+'par'='rotpar'
'rotpar' written backwards gives 'RAPTOR'.
'from' acts as a link.
Can you help me to learn more?
(Other definitions for raptor that I've seen before include "Eagle, hawk, falcon or owl - parrot (anag)" , "Parrot (anag) - bird of prey" , "Harrier possibly" , "Hunter" .)