Most agreeable French resort found by saint (6)
I believe the answer is:
nicest
'most agreeable' is the definition.
(I've seen this in another clue)
'french resort found by saint' is the wordplay.
'french resort' becomes 'nice' (French coastal resort).
'found by' says to put letters next to each other.
'saint' becomes 'st' (abbreviation).
'nice'+'st'='NICEST'
(Other definitions for nicest that I've seen before include "Best" , "most appetising" , "Most appealing" , "Most pleasant or fine" , "Most attractive" .)