Mannequin's exposed hand (5)
I believe the answer is:
dummy
I believe this is a double definition.
'mannequin's' is the first definition.
(I've seen this before)
'exposed hand' is the second definition.
(I've seen this before)
(Other definitions for dummy that I've seen before include "Fool" , "Baby's comforter" , "Pacifier" , "Visible hand of cards" , "Make as if to pass" .)