Calf moving about on bird of prey (6)
I believe the answer is:
falcon
'bird of prey' is the definition.
(falcon is a kind of bird of prey)
'calf moving about on' is the wordplay.
'moving' indicates an anagram.
'about' becomes 'on' (**).
'on' says to put letters next to each other.
'calf' anagrammed gives 'falc'.
'falc'+'on'='FALCON'
(Other definitions for falcon that I've seen before include "Diving bird of prey" , "See 16" , "A hunting bird, may be peregine" , "that's seen flying" , "high-flyer" .)