More pleasant resort — first in Riviera (5)
I believe the answer is:
nicer
'more pleasant' is the definition.
('nice' can be similar in meaning to 'pleasant')
'resort first in riviera' is the wordplay.
'resort' becomes 'nice' (French coastal resort).
'first in riviera' becomes 'r' (nst letter of 'riviera').
'nice'+'r'='NICER'
(Other definitions for nicer that I've seen before include "improved" , "More pleasant or agreeable" , "More pleasing" , "More pleasant, French resort close to Montpellier" , "relatively pleasant" .)