Appalling mutterer? Pa must get a hearing aid! (3,7)
I believe the answer is:
ear trumpet
'a hearing aid' is the definition.
('ear trumpet' can be a synonym of 'hearing aid')
'appalling mutterer? pa' is the wordplay.
'appalling' indicates an anagram (I've seen this in other clues).
'mutterer'+'pa'='muttererpa'
'muttererpa' with letters rearranged gives 'EAR-TRUMPET'.
'must get' is the link.
(Other definitions for ear trumpet that I've seen before include "Former hearing aid" , "Primitive hearing aid" , "help in reception" , "One gathering sound" , "sound engineering device" .)