Signal fire or light (6)
I believe the answer is:
beacon
This clue is a double definition.
'signal fire' is the first definition.
(I've seen this before)
'light' is the second definition.
(I've seen this before)
(Other definitions for beacon that I've seen before include "Warning fire or signal" , "Shining light (on top of a hill?)" , "Warning light on hill or cliff" , "Fire on a hill, lit as a signal" , "A warning light as on headland" .)