Sign bishop invested in currency once (5)
I believe the answer is:
libra
'sign' is the definition.
(sign of the zodiac)
'bishop invested in currency once' is the wordplay.
'bishop' becomes 'b' (abbreviation used in chess).
'invested in' is an insertion indicator.
'currency once' becomes 'lira' (former Italian currency).
'b' inserted inside 'lira' is 'LIBRA'.
(Other definitions for libra that I've seen before include "Person born under Scales sign" , "The Scales in astrology" , "Old pound" , "Scales constellation" , "House" .)