Stupid people undone by this flaw? (8)

I believe the answer is:

halfwits

'stupid people' is the definition.

'undone by this flaw?' is the wordplay.
'undone by' indicates anagramming the letters (the original order of letters must be undone).
'this'+'flaw'='thisflaw'
'thisflaw' is an anagram of 'HALFWITS'.

I've seen this clue in The Guardian.

Want a hint initially instead of a full solution? Install my app