The rest of the canvas (5)
I believe the answer is:
easel
'the canvas' is the definition.
(thesaurus)
'the rest' is the wordplay.
I cannot really see how this works, but
'rest' could be 'ease' (synonyms) and 'ease' is present in the answer.
A single letter 'l' remains which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'of' acts as a link.
Can you help me to learn more?
(Other definitions for easel that I've seen before include "Artist's canvas holder" , "Artist's stand for painting" , "Painter's stand" , "Support for artist's canvas" , "Blackboard supporter" .)