What models do to be seated (3)
I believe the answer is:
sit
'be seated' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for sit that I've seen before include "Order dog to behave" , "Use a chair" , "Take a seat; pose" , "Be sedentary" , "Rest on one's haunches" .)