Supposed to have set (4)
I believe the answer is:
pose
'set' is the definition.
(I know that set can be written as pose)
'supposed to have' is the wordplay.
'to have' indicates a hidden word.
'POSE' is hidden within 'supposed'.
(Other definitions for pose that I've seen before include "Arrange, model" , "'Present, a problem say (4)'" , "Pretend; model" , "Sit; attitude" , "Models do it for photographic or artistic purposes" .)