Is commercial old god a dancer? (7)
I believe the answer is:
isadora
'a dancer?' is the definition.
(I have seen 'Famous dancer' mean 'isadora' so perhaps 'dancer' could also mean 'isadora')
'is commercial old god' is the wordplay.
'commercial' becomes 'ad' (abbreviation for advertisement).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'god' becomes 'ra' (Egyptian god).
'is'+'ad'+'o'+'ra'='ISADORA'
(Other definitions for isadora that I've seen before include "-- Duncan, American dancer" , "girl" , "woman's name" , "- Duncan, twentieth century US dancer" , "Famous dancer" .)