It's naive to refrigerate unfinished food (8)
I believe the answer is:
childish
'it's naive' is the definition.
(thesaurus)
'refrigerate unfinished food' is the wordplay.
'refrigerate' becomes 'chill' (I've seen this in another clue).
'unfinished' means to remove the last letter.
'food' becomes 'dish' (dish is a kind of food).
'chill' with its last letter taken off is 'chil'.
'chil'+'dish'='CHILDISH'
'to' is the link.
(Other definitions for childish that I've seen before include "Juvenile" , "Silly, immature" , "Puerile" .)