Fine old instrument used to make glass (5)
I believe the answer is:
flute
'glass' is the definition.
(flute is a kind of glass)
'fine old instrument' is the wordplay.
'fine' becomes 'f' (abbreviation).
'old instrument' becomes 'lute' (I've seen this before**).
'f'+'lute'='FLUTE'
'used to make' is the link.
(Other definitions for flute that I've seen before include "Narrow wineglass" , "Musical instrument - wineglass" , "Wine glass; instrument" , "Blown" , "High-pitched woodwind instrument" .)