Yawning in public (4)
I believe the answer is:
open
I believe this is a double definition.
'yawning' is the first definition.
(similar in meaning)
'public' is the second definition.
(similar in meaning)
'in' acts as a link.
(Other definitions for open that I've seen before include "Honest - frank" , "Available for business, exposed" , "still in debate" , "Frank - accessible" , "Undo; exposed to attack" .)