Gaping (4)
'gaping' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for wide-open that I've seen before include "Gaping -- very vulnerable" , "Exposed to attack" , "Vulnerable to attack (colloq.)" .)
'gaping' is the definition.
('yawn' can be a synonym of 'gape')
This is the entire clue.
(Other definitions for yawning that I've seen before include "Gaping wide open" , "Cavernous" , "Displaying tiredness" , "showing sign of tiredness?" , "Wide open (as chasm)" .)
'gaping' is the definition.
(thesaurus)
This is all the clue.
(Other definitions for ajar that I've seen before include "Not to answer" , "Fractionally open" , "Not quite shut" , "A litle bit open" , "partly opened" .)