Artist is a noodler, sadly (8)
I believe the answer is:
'artist' is the definition.
(Leonardo is an example)
'a noodler sadly' is the wordplay.
'sadly' indicates an anagram.
'anoodler' is an anagram of 'LEONARDO'.
'is' is the link.
(Other definitions for leonardo that I've seen before include "and 12 Across: Renaissance genius" , "Renaissance man" , "Great Italian artist ........ da Vinci" , "Great painter of the Mona Lisa, . . . . . . . . da Vinci" , ". . . . . . . . da Vinci (Renaissance genius)" .)