He uses a favourite ear-piece (4)
I believe the answer is:
pete
'he' is the definition.
'a favourite ear-piece' is the wordplay.
'a favourite' becomes 'pet' (synonyms).
'ear-piece' becomes 'e' (this could be a standard abbreviation I've not previously seen).
'pet'+'e'='PETE'
'uses' acts as a link.
Can you help me to learn more?
(Other definitions for pete that I've seen before include "- Doherty, Babyshambles singer" , "Small 14 [PETER JONES]" , "filmed with his 1 across [DRAGON]" , "- Sampras, tennis star" , "For his sake" .)