Suffer with a bitter feeling, not one that will afflict you for ever (9)
I believe the answer is:
incurable
'that will afflict you for ever' is the definition.
'suffer with a bitter feeling not one' is the wordplay.
'suffer' becomes 'incur' (I've seen this before**).
'with' means one lot of letters go next to another.
'bitter feeling' becomes 'bile'.
'not' is a deletion indicator.
'one' becomes 'i' (Roman numeral).
'bile' with 'i' removed is 'ble'.
'incur'+'a'+'ble'='INCURABLE'
(Other definitions for incurable that I've seen before include "Incorrigible" , "Not able to be made well" , "must be endured" , "Beyond reach of treatment" .)