Deluded shop venture ends in failure (5)
I believe the answer is:
duped
'deluded' is the definition.
(duping is a kind of deluding)
'shop venture ends in failure' is the wordplay.
'ends' indicates one should take the final letters.
'in' means one lot of letters goes inside another.
'failure' becomes 'dud' (dud is a kind of failure).
The last letters of 'shop venture' are 'pe'.
'pe' going inside 'dud' is 'DUPED'.
(Other definitions for duped that I've seen before include "Fooled, codded" , "Hoodwinked and misled" , "Tricked" , "Cheated" , "Taken for a ride" .)