It's easy to swindle Oscar for one (6)
I believe the answer is:
doddle
'one' is the definition.
Both the definition and answer are singular nouns.
Maybe there's an association between them I don't understand?
'it's easy to swindle oscar' is the wordplay.
I cannot quite understand how this works, but
'swindle' could be 'do' and 'do' is found in the answer.
'it' could be 'e' ('e' can mean 'electronic' which is similar to 'IT') and 'e' is found within the answer.
This explanation may well be incorrect...
'for' is the link.
Can you help me to learn more?
(Other definitions for doddle that I've seen before include "gift" , "pushover" , "Easy task (informal)" , "Easy crossword?" , "Absurdly simple" .)