US marshal to carry impediment to hearing (7)
I believe the answer is:
earplug
'us marshal to carry' is the definition.
I can't tell whether this definition defines the answer.
'impediment to hearing' is the wordplay.
'impediment' becomes 'plug' (plug is a kind of impediment).
'to' means one lot of letters go next to another (I've seen this in other clues).
'hearing' becomes 'ear' (ear is a kind of hearing).
'plug' after 'ear' is 'EARPLUG'.
Can you help me to learn more?
(Other definitions for earplug that I've seen before include "It's used to prevent entry of noise or water" , "Noise defender" , "Noise excluder" , "It stops racket" , "Block" .)