Nest on a crest (5)
I believe the answer is:
aerie
'nest on a crest' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for aerie that I've seen before include "inaccessible place" , "wherein some types of bird may sit" , "Visionary" , "Sort of nest" , "lofty dwelling" .)