Fed up about American unwilling to listen (4)
I believe the answer is:
deaf
'unwilling to listen' is the definition.
(I've seen this in another clue)
'fed up about american' is the wordplay.
'up' is a reversal indicator (in down clue: letters go upwards).
'about' indicates putting letters inside.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'fed' back-to-front is 'def'.
'def' enclosing 'a' is 'DEAF'.
(Other definitions for deaf that I've seen before include "Lacking hearing" , "Audibly challenged" , "Aurally challenged" , "Hard of hearing" , "Receiving no sound" .)