The pound sign (5)
I believe the answer is:
libra
This clue is a double definition.
'the pound' is the first definition.
(I've seen this before)
'sign' is the second definition.
(sign of the zodiac)
(Other definitions for libra that I've seen before include "Zodiac sign of the scales" , "stars" , "Balance constellation" , "Person born under Scales sign" , "House" .)