Shortly rate stupid people (5)
I believe the answer is:
asses
'stupid people' is the definition.
(I've seen this before)
'shortly rate' is the wordplay.
'shortly' means to remove the last letter.
'rate' becomes 'assess' (to assess is to rate or evaluate).
'assess' with its final letter taken off is 'ASSES'.
(Other definitions for asses that I've seen before include "Fools; animals" , "Braying animals" , "Jennets" , "Hardy and sure-footed animals" , "Fools; beasts of burden" .)