City of noted square singer who lit up sick soldiers (8)
I believe the answer is:
florence
This clue is a double definition.
'city of noted square' is the first definition.
(Florence is famous for various piazzas or squares)
'singer who lit up sick soldiers' is the second definition.
(Florence Nightingale, 'the Lady of the Lamp')
(Other definitions for florence that I've seen before include "City on R. Arno" , "The familiar Miss Nightingale, famous nurse" , "Italian city; Magic Roundabout character" , "Italian city, noted art centre" , "place in Italy" .)