Painter's title describing witch (7)
I believe the answer is:
chagall
'painter's' is the definition.
(Marc Chagall)
'title describing witch' is the wordplay.
'title' becomes 'call' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'describing' indicates putting letters inside (describe can mean to form the outline of).
'witch' becomes 'hag' (synonyms).
'call' going around 'hag' is 'CHAGALL'.
Can you help me to learn more?
(Other definitions for chagall that I've seen before include "Marc --, Russian-French artist" , "He painted" , "Marc --, Russian artist" , "Russian-born painter" , "Marc -, twentieth century Russian-born French artist" .)