Speculation, with gold being held by those people (6)
I believe the answer is:
theory
'speculation' is the definition.
(thesaurus)
'gold being held by those people' is the wordplay.
'gold' becomes 'or' ('or' is the heraldic name for gold).
'being held by' means one lot of letters goes inside another.
'those people' becomes 'they' (I've seen this before).
'or' put inside 'they' is 'THEORY'.
'with' is the link.
(Other definitions for theory that I've seen before include "Opinion or supposition to explain something" , "Scientific supposition" , "Set of principles on which practice is based" , "Scientific conjecture" , "Explanation of a phenomenon" .)