Two instruments for sailors' dance (8)
I believe the answer is:
hornpipe
'sailors' dance' is the definition.
(I've seen this in another clue)
'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' acts as a link.
(Other definitions for hornpipe that I've seen before include "piece of music for an > old dance" , "Lively old sailors' dance" , "Lively solo dance associated with sailors" , "Obsolete instrument: naval dance" , "Lively jig" .)