Face in sleep turning over (3)
I believe the answer is:
pan
'face' is the definition.
('pan' is old-fashioned US slang for 'face')
'sleep turning over' is the wordplay.
'sleep' becomes 'nap' (a nap is a short sleep).
'turning over' shows that the letters should be reversed in order.
'nap' in reverse letter order is 'PAN'.
'in' is the link.
(Other definitions for pan that I've seen before include "Slate - cooking vessel" , "Pot" , "God of herds with merry merry pipes" , "Peter . . ., Barrie's immortal boy" , "Cooking utensil and Greek god" .)