Guard caught bird of prey, covering head (6)
I believe the answer is:
captor
'guard' is the definition.
(I've seen this before)
'covering head' is the wordplay.
'covering' becomes 'cap' (cap is a kind of covering).
'head' becomes 'tor' (I am not sure about this - if you are sure you should believe this answer much more).
'cap'+'tor'='CAPTOR'
'caught bird of prey' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for captor that I've seen before include "One takes prisoners" , "One imprisoning another" , "One confining another" , "Top car (anag) -- jailer" , "He catches someone" .)