Guess or gamble (9)
I believe the answer is:
speculate
I believe this is a double definition.
'guess' is the first definition.
(I know that guess is a more specific form of speculate)
'gamble' is the second definition.
(thesaurus)
(Other definitions for speculate that I've seen before include "Play the market" , "Make conjectures" , "Imagine" , "Gamble on investments" , "Bet; theorise" .)