Support for artist getting traitor beheaded (5)
I believe the answer is:
easel
'support for artist' is the definition.
(I've seen this before)
'traitor beheaded' is the wordplay.
'traitor' becomes 'weasel' (weasel can mean a treacherous person).
'beheaded' means to remove the first letter (the head of the word is removed).
'weasel' with its first letter taken off is 'EASEL'.
'getting' is the link.
(Other definitions for easel that I've seen before include "Wooden frame for an artist" , "art supporter" , "Support for artist's canvas" , "Picture stand" , "Constable's stand?" .)