Check car's temperature (5)
I believe the answer is:
audit
'check' is the definition.
(thesaurus)
'car's temperature' is the wordplay.
'car' becomes 'audi' (audi is a german car brand).
'temperature' becomes 't' (abbreviation).
'audi'+'t'='AUDIT'
(Other definitions for audit that I've seen before include "Examine accounts" , "Thoroughgoing check" , "Verify accounts" , "vetting of books" , "Review firm's accounts, annual check" .)