One likely to succeed in search for gold (8)
I believe the answer is:
prospect
I believe this is a double definition.
'one likely to succeed' is the first definition.
(as in a likely prospect)
'search for gold' is the second definition.
(to prospect is to search for minerals such as gold)
'in' acts as a link.
(Other definitions for prospect that I've seen before include "Someone who might buy" , "Search for gold - view - scene - probability" , "Survey the outlook" , "Gray distantly associated with Eton College" , "Possibility; wide view" .)