Crooner posed to accommodate cool artist (7)
I believe the answer is:
sinatra
'crooner' is the definition.
(I know that Sinatra is a crooner)
'posed to accommodate cool artist' is the wordplay.
'posed' becomes 'sat' (posed or sat for an artist).
'to accommodate' means one lot of letters goes inside another.
'cool' becomes 'in' ('in' can mean fashionable or cool).
'artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
'sat' going around 'in' is 'sinat'.
'sinat'+'ra'='SINATRA'
(Other definitions for sinatra that I've seen before include "'Old Blue Eyes'" , "Frank -, twentieth century US singer" , "Francis Albert did it his way" , "Something of a strain for top crooner" , "Frank . . . . . . ., late great popular singer" .)