In the morning, stared after leaving girl stunned (6)
I believe the answer is:
amazed
'stunned' is the definition.
(synonyms)
'in the morning stared after leaving girl' is the wordplay.
'in the morning' becomes 'am' (AM on a clock).
'stared' becomes 'gazed' ('gaze' can be a synonym of 'stare').
'after leaving' indicates named letters should be taken away.
'girl' becomes 'g'.
'gazed' with 'g' taken away is 'azed'.
'am'+'azed'='AMAZED'
(Other definitions for amazed that I've seen before include "Greatly surprised or astonished" , "Overwhelmed with wonder" , "Astonished, stunned" , "Awe-struck" , "Gobsmacked" .)