Perfectly clean cooking utensil the French kept on board (8)
I believe the answer is:
spotless
'perfectly clean' is the definition.
(I've seen this before)
'cooking utensil the french kept on board' is the wordplay.
'cooking utensil' becomes 'pot' (pot is a kind of cooking utensil).
'the french' becomes 'les' (plural form of 'the' in French).
'kept' is an insertion indicator.
'on board' becomes 'ss' (I've seen this in other clues).
'pot'+'les'='potles'
'potles' going inside 'ss' is 'SPOTLESS'.
(Other definitions for spotless that I've seen before include "Without a mark, completely clean" , "Extremely clean" , "Perfect" , "honest!" , "showing no sign of acne?" .)