He’d admit adopting old dance (7)
I believe the answer is:
hoedown
'dance' is the definition.
(I've seen this before)
'he'd admit adopting old' is the wordplay.
'admit' becomes 'own' (I've seen this before).
'adopting' means one lot of letters goes inside another.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'hed'+'own'='hedown'
'hedown' placed around 'o' is 'HOEDOWN'.
(Other definitions for hoedown that I've seen before include "US folk dance gathering" , "Boisterous American folk dance" , "US party" , "Hillbilly dance" , "American country dance" .)