Painter's sitter so fidgety (8)
I believe the answer is:
rossetti
'painter's' is the definition.
(I've seen this before)
'sitter so fidgety' is the wordplay.
'sitter so' can be anagrammed to 'ROSSETTI'.
Though, I am not sure how the anagram is indicated.
Can you help me to learn more?
(Other definitions for rossetti that I've seen before include "She wroteBleak Midwinter" , "Christina -, nineteenth century century English poet" , "Artist" , "English Pre-Raphaelite poet and painter, d. 1882" , "Dante Gabriel --, English poet/painter" .)