Oscar avoiding comparatively humourless artist (5)
I believe the answer is:
durer
'artist' is the definition.
(I've seen this before)
'oscar avoiding comparatively humourless' is the wordplay.
'oscar' becomes 'O' (phonetic alphabet: alpha, bravo, charlie etc.).
'avoiding' suggests deleting specific letters.
'comparatively humourless' becomes 'dourer' (dour means gloomy or humourless).
'dourer' with 'o' taken away is 'DURER'.
(Other definitions for durer that I've seen before include "Albrecht --, German painter and engraver" , "German artist, d. 1528" , "Albrecht -, Ger. artist" , "Picture-maker" , "Old master" .)