Boy having to name a dance (10)
I believe the answer is:
charleston
'a dance' is the definition.
(charleston is a kind of dance)
'boy having to name' is the wordplay.
'boy' becomes 'charles' (**).
'having' is a charade indicator (letters next to each other).
'name' becomes 'n' (common abbreviation e.g. on forms).
'charles'+'to'+'n'='CHARLESTON'
(Other definitions for charleston that I've seen before include "Lively 1920s' dance" , "American port" , "US city - 1920s' dance" , "Dance making" , "Lively dance - then carols (anag)" .)