Composer and novelist, but not a painter (2,5)
I believe the answer is:
el greco
'painter' is the definition.
(nickname of Domenikos Theotokpoulos, 1541-1641)
'composer and novelist but not a' is the wordplay.
'composer' becomes 'elgar' (Edward Elgar).
'and' becomes 'n' (common abbreviation for 'and').
'novelist' becomes 'eco' (Umberto Eco).
'but not' indicates named letters should be taken away.
'a' becomes 'an'.
'elgar'+'n'+'eco'='elgarneco'
'elgarneco' with 'an' taken away is 'EL GRECO'.
(Other definitions for el greco that I've seen before include "Spanish painter born 1541 in Crete" , "Famous painter's nickname" , "Sixteenth to seventeenth century Greek-born Spanish painter" , "Greek born Spanish painter" , "Crete-born Sp. painter" .)