Comment: make a new rating! (6)
I believe the answer is:
remark
'comment' is the definition.
(a remark is a spoken comment)
'a new rating' is the wordplay.
'a new' becomes 're' (I can't explain this - if you can you should give a lot more credence to this answer).
'rating' becomes 'mark' (mark is a kind of rating).
're'+'mark'='REMARK'
'make' acts as a link.
Can you help me to learn more?
(Other definitions for remark that I've seen before include "Notice or comment on" , "Written or spoken comment" , "Something said; take notice of" , "Comment or mention" , "Incidental observation" .)