Observe the French saints without blemish (8)
I believe the answer is:
spotless
'without blemish' is the definition.
(I've seen this before)
'observe the french saints' is the wordplay.
'observe' becomes 'spot' (I've seen this before**).
'the french' becomes 'le'.
'saints' becomes 'ss'.
'spot'+'le'+'ss'='SPOTLESS'
(Other definitions for spotless that I've seen before include "Without blemish" , "Immaculate" , "Extremely clean" , "honest!" , "Fully clean" .)