Stick with large work of art (6)
I believe the answer is:
pastel
'work of art' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'stick with large' is the wordplay.
'stick' becomes 'paste' (as in sticking or pasting something down).
'with' means one lot of letters go next to another.
'large' becomes 'L' (eg in clothes sizes).
'paste'+'l'='PASTEL'
Can you help me to learn more?
(Other definitions for pastel that I've seen before include "Delicate colour found in plates" , "Chalky crayon" , "Soft shade; crayon" , "Type of crayon" , "Outmoded" .)