Stick up some simpleton (3)
I believe the answer is:
mug
This clue is a double definition.
'stick up' is the first definition.
(mugging is a kind of sticking up)
'simpleton' is the second definition.
(I've seen this before)
'some' acts as a link.
(Other definitions for mug that I've seen before include "Drinking vessel for one easily deceived" , "Drinking vessel, by gum" , "Fall guy" , "attack" , "In slang, a person easily deceived" .)