Exclamation of contempt by stupid person (5)
I believe the answer is:
booby
'stupid person' is the definition.
(I've seen this before)
'exclamation of contempt by' is the wordplay.
I cannot really understand how this works, but
'exclamation' could be 'boo' (I have seen 'Exclamation of disapproval ' mean 'boo' so perhaps 'exclamation' could also mean 'boo') and 'boo' is located in the answer.
'by' is found in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for booby that I've seen before include "Pink-footed seabird" , "Dunce" , "Sort of trap" , "Stupid person" , "marine bird" .)