Relish old dance (5)
I believe the answer is:
tango
'dance' is the definition.
(tangoing is a kind of dancing)
'relish old' is the wordplay.
'relish' becomes 'tang' ('tang' can be a synonym of 'relish').
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'tang'+'o'='TANGO'
(Other definitions for tango that I've seen before include "Letter T in radio comms" , "Latin-American dance - code for T" , "Dance of South American origin" , "Dance originally from Buenos Aires" , "Dance music" .)