Serve time inside lighthouse, maybe? (6)
I believe the answer is:
beacon
This could be a double definition.
'serve time' is the first definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'lighthouse maybe?' is the second definition.
(I know that lighthouse is a type of beacon)
'inside' acts as a link.
Can you help me to learn more?
(Other definitions for beacon that I've seen before include "Warning light on hilltop" , "Warning, guiding, fire" , "Hill fire seen from a distance" , "Warning light on tower or hill" , "This may serve as a warning" .)