Music for two instruments (8)
I believe the answer is:
hornpipe
'music' is the definition.
(hornpipe is a kind of music)
'two instruments' is the wordplay.
'two instruments' can mean two substitutions for 'instrument'.
'instrument' becomes 'horn'.
'instrument' becomes 'pipe' (pipe is a kind of instrument).
'horn'+'pipe'='HORNPIPE'
'for' is the link.
(Other definitions for hornpipe that I've seen before include "Lively solo dance associated with sailors" , "Lively jig" , "Lively old sailors' dance" , "Obsolete instrument: naval dance" , "piece of music for an > old dance" .)