Ear about to sense upset with great pleasure (7)
I believe the answer is:
gleeful
'with great pleasure' is the definition.
'ear about to sense upset' is the wordplay.
'ear' becomes 'lug' (informal term for an ear).
'about' indicates putting letters inside.
'to sense' becomes 'feel' ('feel' can be a synonym of 'sense'**).
'upset' is a reversal indicator.
'lug' enclosing 'feel' is 'lufeelg'.
'lufeelg' backwards is 'GLEEFUL'.
(Other definitions for gleeful that I've seen before include "Exuberantly joyous" , "Cheerful" , "Exuberantly joyful" , "Happy" , "Jubilant" .)