Simpleton’s one point taking one in (5)
I believe the answer is:
idiot
'simpleton's' is the definition.
(idiot is a kind of simpleton)
'one point taking one in' is the wordplay.
'one' becomes 'i' (Roman numeral).
'point' becomes 'dot' ('dot' can be a synonym of 'point'**).
'taking' means one lot of letters go next to another.
'one' becomes 'i' (Roman numeral).
'in' means one lot of letters goes inside another.
'i'+'dot'='idot'
'idot' going around 'i' is 'IDIOT'.
(Other definitions for idiot that I've seen before include "Twit" , "Steal small amount" , "Dostoevsky hero" , "Dipstick" , "Silly ass" .)