Disbelief at seeing he is taken in by cash machine (7)
I believe the answer is:
atheism
'disbelief' is the definition.
(thesaurus)
'seeing he is taken in by cash machine' is the wordplay.
'seeing he' becomes 'he'.
'taken in by' means one lot of letters goes inside another.
'cash machine' becomes 'atm' ('ATM' can be a synonym of 'cash machine').
'he'+'is'='heis'
'heis' put within 'atm' is 'ATHEISM'.
'at' acts as a link.
(Other definitions for atheism that I've seen before include "displaying opposition to religion" , "Lack of belief in the existence of God" , "A lack of faith" , "Owed" , "Non-belief in God" .)