Dance with uncle, a bachelor (5)
I believe the answer is:
samba
'dance' is the definition.
(Brazilian dance)
'with uncle a bachelor' is the wordplay.
'with' means one lot of letters go next to another.
'uncle' becomes 'sam' (Uncle Sam is an example).
'a bachelor' becomes 'BA' (abbreviation for Bachelor of Arts degree).
'sam' put next to 'ba' is 'SAMBA'.
(Other definitions for samba that I've seen before include "Latin dance" , "Brazilian dance" , "South American dance" , "Lively ballroom dance from Brazil" , "Dance music" .)