Priest regularly scrutinised renovated car part (7)
I believe the answer is:
retread
'renovated car part' is the definition.
(a tyre that's been retreaded)
'priest regularly scrutinised' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'scrutinised' becomes 'read'.
The alternate letters of 'priest' are 'ret'.
'ret'+'read'='RETREAD'
(Other definitions for retread that I've seen before include "Recover" , "Second-hand tyre" , "Revamped Michelin" , "Remoulded tyre" , "Go back over (one's route) - mend(ed) tyre" .)