Sit — pose (5)
I believe the answer is:
model
I believe this clue is a double definition.
'sit' is the first definition.
(I know that sit can be written as model)
'pose' is the second definition.
(I know that pose can be written as model)
(Other definitions for model that I've seen before include "She saunters on the catwalk" , "Exemplary - mannequin" , "Perfect" , "Small-scale representation" , "Fashion - prototype" .)