Did Judy Garland paint a portrait of James Cagney dressed as a clown?

Answer 1

Judy was not a painter. She was, however, a pretty good writer as seen in her poetry.
http://www.thejudyroom.com/poems.html

I have never heard that she painted any portrait of anything and I have done extensive research on her and read almost all there is to read on/about her. :)

Answer 2

She is not known for her paintings...I doubt she did any painting or at least some of it would be in her 'own' museum.

So as hard as it is to prove a negative statement my answer is:
No, very unlikely.