Schemer heading off with yen for risky operation (7)
I believe the answer is:
lottery
'risky operation' is the definition.
(I've seen this before)
'schemer heading off with yen' is the wordplay.
'schemer' becomes 'plotter' ('plotter' can be a synonym of 'schemer').
'heading off' means to remove the first letter.
'with' says to put letters next to each other.
'yen' becomes 'y'.
'plotter' with its initial letter taken off is 'lotter'.
'lotter'+'y'='LOTTERY'
'for' acts as a link.
(Other definitions for lottery that I've seen before include "Chance competition" , "Random prize game" , "Gambling game" , "Matter of chance" , "Risky operation" .)