Gambler's quest (6)
I believe the answer is:
system
'gambler's quest' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for system that I've seen before include "Group of elements forming a unified whole" , "Method of operating" , "Arrangement of parts that function together" , "Organised whole made up of related parts" , "Method of organization" .)