Hapless or amusing dimwit (9)
I believe the answer is:
ignoramus
'dimwit' is the definition.
(I've seen this before)
'hapless or amusing' is the wordplay.
'hapless' indicates anagramming the letters.
'or'+'amusing'='oramusing'
'oramusing' with letters rearranged gives 'IGNORAMUS'.
(Other definitions for ignoramus that I've seen before include "A know-nothing" , "At the present time" , "unwitting person" , "Simpleton" , "Uneducated person" .)