Principal motor noise the French raised (8)
I believe the answer is:
cardinal
'principal' is the definition.
(thesaurus)
'motor noise the french raised' is the wordplay.
'motor' becomes 'car' (I've seen this before).
'noise' becomes 'din' (din is a kind of noise).
'the french' becomes 'la'.
'raised' says the letters should be written in reverse.
'la' reversed gives 'al'.
'car'+'din'+'al'='CARDINAL'
(Other definitions for cardinal that I've seen before include "Red - chief - RC dignitary" , "fundamental importance" , "Vivid red of a senior bishop?" , "papal adviser" , "Prince of the RC church" .)