Bettor's adviser (7)
I believe the answer is:
tipster
'bettor's adviser' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for tipster that I've seen before include "One providing betting hints" , "One with views on race" , "Supposed expert on horses" , "he recommends risky investments" , "One advising betters" .)