Jeer from stupid person (5)
I believe the answer is:
booby
'stupid person' is the definition.
(I've seen this before)
'jeer from' is the wordplay.
'jeer' becomes 'boo' (I've seen this in another clue).
'from' becomes 'by' (by can mean from a particular person).
'boo'+'by'='BOOBY'
(Other definitions for booby that I've seen before include "Pink-footed seabird" , "Gannet" , "Stupid person" , "Dunce" , "Sort of trap" .)