Eagles' nests (6)
I believe the answer is:
eyries
'eagles' nests' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for eyries that I've seen before include "Lofty nest of birds of prey" , "Lofty nests of a bird of prey" , "Lofty nests of birds of prey" , "Lofty nests for eagles" , "Eagle's nest" .)