Employed in nightclub as solo singer (5)
I believe the answer is:
basso
'singer' is the definition.
(Italian term for a bass singer)
'employed in nightclub as solo' is the wordplay.
'employed in' indicates a hidden word.
'BASSO' is hidden within 'nightclub as solo'.
(Other definitions for basso that I've seen before include "Singer" , "one's deep in sound" , "low voice" , "Lowest male singing voice (sometimes 'profundo')" .)