Singer with glasses in front of new instrument (7)
I believe the answer is:
bassoon
'instrument' is the definition.
(bassoon is a kind of instrument)
'singer with glasses in front of new' is the wordplay.
'singer' becomes 'bass' (bass is a kind of singer**).
'with' says to put letters next to each other.
'glasses' becomes 'oo' (OO looks like spectacles).
'in front of' suggests taking the first letters.
The initial letter of 'new' is 'n'.
'bass'+'oo'+'n'='BASSOON'
(Other definitions for bassoon that I've seen before include "wind player" , "Double-reed instrument" , "Low wind instrument" , "Instrument - no ASBOs (anag)" , "Large woodwind instrument" .)