Hid gear in a broken amplifier (7,3)
I believe the answer is:
hearing aid
'amplifier' is the definition.
(thesaurus)
'hid gear in a broken' is the wordplay.
'broken' indicates an anagram.
'hid'+'gear'+'in'+'a'='hidgearina'
'hidgearina' with letters rearranged gives 'HEARING-AID'.
(Other definitions for hearing aid that I've seen before include "Earpiece" , "asset in court?" , "Help for the partially deaf" , "Ear trumpet" , "Amplifier for ear" .)