Perfect sitter (5)
I believe the answer is:
model
I believe this is a double definition.
'perfect' is the first definition.
(I've seen this before)
'sitter' is the second definition.
(I know that model is a type of sitter)
(Other definitions for model that I've seen before include "Small-size version" , "She saunters on the catwalk" , "who displays it" , "Miniature replica" , "Clothes displayer" .)