When do old cooks dance? (7)
I believe the answer is:
hoedown
'dance?' is the definition.
(I've seen this before)
'when do old cooks' is the wordplay.
'old' becomes 'o' (abbreviation).
'cooks' indicates anagramming the letters.
'when'+'do'+'o'='whendoo'
'whendoo' anagrammed gives 'HOEDOWN'.
(Other definitions for hoedown that I've seen before include "American dance gathering" , "American country dance" , "US folk dance gathering" , "Square dance" , "US party" .)