Mouth opening in Iraq, seeing desert (4)
I believe the answer is:
gobi
'desert' is the definition.
(I know that Gobi is a desert)
'mouth opening in iraq' is the wordplay.
'mouth' becomes 'gob' (informal term for the mouth).
'opening in' indicates taking the first letters.
The initial letter of 'iraq' is 'i'.
'gob'+'i'='GOBI'
'seeing' acts as a link.
(Other definitions for gobi that I've seen before include "Desert in east Asia" , "Plain" , "Asiatic barren plateau which means 'stony desert'" , "arid area" , "Desert in China/Mongolia; cauliflower (Ind.)" .)