Hilltops (6)
I believe the answer is:
crests
'hilltops' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for crests that I've seen before include "summits" , "Topmost ridges of mountains" , "Tufts on birds' heads, or tops of waves" , "Emblems of families" .)