Rated idiot who mixed seeds (8)
I believe the answer is:
assessed
'rated' is the definition.
(I've seen this in another clue)
'idiot who mixed seeds' is the wordplay.
I cannot quite see how this works, but
'idiot' could be 'ass' (I've seen this in another clue) and 'ass' is found within the answer.
an anagram of 'seeds' is 'essed' which is within the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for assessed that I've seen before include "Appraised" , "Judged the worth of something" , "Estimated" , "Evaluated" , "checked out?" .)