Many turning up old doctor injected, chancy business (7)
I believe the answer is:
tombola
'chancy business' is the definition.
(a tombola is a lottery)
I cannot understand how the rest of the clue works.
(Other definitions for tombola that I've seen before include "Lottery game" , "Game with tickets drawn from a revolving drum" , "Small lottery at fete" , "Kind of lottery draw using a revolving drum" , "Rotating drum game" .)