Dupes four unclothed idiots (7)
I believe the answer is:
outwits
'dupes' is the definition.
Although both the answer and definition are verbs in their -s form, I don't understand how they can define each other.
'four unclothed idiots' is the wordplay.
'unclothed' means to look at the middle letters.
'idiots' becomes 'twits' (I am not sure about this - if you are sure you should believe this answer much more).
The middle letters of 'four' are 'ou'.
'ou'+'twits'='OUTWITS'
Can you help me to learn more?
(Other definitions for outwits that I've seen before include "kids" , "Gulls" , "Is too smart for" .)