An efficient killer to a mother bird of prey (8)
I believe the answer is:
tomahawk
'an efficient killer' is the definition.
'tomahawk' can be an answer for 'killer' (I've seen this before). I am unsure of the 'an efficient' bit.
'to a mother bird of prey' is the wordplay.
'a mother' becomes 'ma' (Ma is another word for mother or mum).
'bird of prey' becomes 'hawk' (hawk is a kind of bird of prey).
'to'+'ma'+'hawk'='TOMAHAWK'
Can you help me to learn more?
(Other definitions for tomahawk that I've seen before include "Brave's hatchet" , "Brave's arm" , "intended to make a kill" , "Light native axe" , "its strike can be fatal" .)