Less enthusiastic about a new riddle (8)
I believe the answer is:
colander
'riddle' is the definition.
(thesaurus)
'less enthusiastic about a new' is the wordplay.
'less enthusiastic' becomes 'colder'.
'about' means one lot of letters goes inside another.
'a new' becomes 'an' (I've seen this in other clues).
'colder' going around 'an' is 'COLANDER'.
(Other definitions for colander that I've seen before include "Container for straining water from food" , "Kitchen item" , "Leaky vessel" , "Food strainer" , "It is used to strain water from food" .)