Turner’s offer to artist? No offer, ultimately (5)
I believe the answer is:
'turner's' is the definition.
(something that turns)
'offer to artist? no offer ultimately' is the wordplay.
'ultimately' indicates one should take the final letters.
The last letters of 'offer to artist no offer' are 'ROTOR'.
(Other definitions for rotor that I've seen before include "Revolving bar" , "Revolving blade (as on helicopter)" , "It goes round and round (and back and forth)" , "Eddy" , "Revolving arm in machine" .)