Nancy turns out to be shrewd (5)
I believe the answer is:
canny
'to be shrewd' is the definition.
(both can mean having good judgement)
'nancy turns' is the wordplay.
'turns' indicates anagramming the letters.
'nancy' anagrammed gives 'CANNY'.
'out' acts as a link.
(Other definitions for canny that I've seen before include "Shrewd like Scotsman" , "Astute" , "Worldly-wise" , "Shrewd, clever" , "Shrewd, knowing" .)