More pleasant resort on river (5)
I believe the answer is:
nicer
'more pleasant' is the definition.
('nice' is associated in meaning with 'pleasant')
'resort on river' is the wordplay.
'resort' becomes 'nice' (French coastal resort).
'on' says to put letters next to each other (in a down clue, letters appear on others).
'river' becomes 'r' (abbreviation).
'nice'+'r'='NICER'
(Other definitions for nicer that I've seen before include "More pleasant or fine" , "Pleasanter" , "relatively pleasant" , "more lovely" , "More pleasing" .)