Sinatra's working, making number exciting, principally for dancer (7)
I believe the answer is:
astaire
'for dancer' is the definition.
(I've seen this before)
'sinatra's working making number exciting principally' is the wordplay.
I cannot really understand how this works, but
'number' could be 'air' (I have seen 'A number' mean 'air' so perhaps 'number' could also mean 'air') and 'air' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for astaire that I've seen before include "US dancer (Top Hat)" , "dance performer" , "Fred - - (films)" , "Fred -, twentieth century US dancer" , "A satire about Fred, great Hollywood dancer" .)