A quiet fellow in protective garment (5)
I believe the answer is:
apron
'protective garment' is the definition.
(apron is a kind of protective garment)
'a quiet fellow' is the wordplay.
'quiet' becomes 'p' (music symbol for 'piano', ie soft or quiet).
'fellow' becomes 'ron' (masculine given name).
'a'+'p'+'ron'='APRON'
'in' is the link.
(Other definitions for apron that I've seen before include "conveyor-belt" , "item of protective clothing" , "area in front of aircraft hangar" , "Protective garment worn at front" , "Pinny -part of the fairway leading onto the green" .)