Gold thread primarily used in fashion house, one hears (7)
I believe the answer is:
auditor
'one hears' is the definition.
(a person who hears is an auditor)
'gold thread primarily used in fashion house' is the wordplay.
'gold' becomes 'au' (Au is the chemical symbol for gold).
'primarily' indicates taking the first letters.
'used in' indicates putting letters inside.
'fashion house' becomes 'dior' (I've seen this in other clues).
The first letter of 'thread' is 't'.
't' inserted into 'dior' is 'ditor'.
'au'+'ditor'='AUDITOR'
(Other definitions for auditor that I've seen before include "Financial checker" , "Examiner of accounts" , "Account inspector" , "Accounts checker" , "Person who listens" .)