Noisily wear out part of car (4)
I believe the answer is:
tyre
'part of car' is the definition.
(I've seen this before)
'noisily wear out' is the wordplay.
'noisily' shows a homophone (sound like).
'wear out' becomes 'tire' (synonyms).
'tire' sounds like 'TYRE'.
(Other definitions for tyre that I've seen before include "Band on wheel" , "Biblical town" , "Rubber wheel rim" , "Ancient (and modern) port - rim for wheel" , "Pneumatic wheel cover" .)