Singer in boater, dancing (8)
I believe the answer is:
baritone
'singer' is the definition.
(baritone is a kind of singer)
'in boater dancing' is the wordplay.
'dancing' indicates an anagram.
'in'+'boater'='inboater'
'inboater' with letters rearranged gives 'BARITONE'.
(Other definitions for baritone that I've seen before include "Male singer between tenor and bass" , "Male singer looks odd in boater" , "solo voice" , "Male voice between bass and tenor" , "Male singer in boater, strangely" .)