Conjecture made by those people importing gold (6)
I believe the answer is:
theory
'conjecture' is the definition.
(thesaurus)
'those people importing gold' is the wordplay.
'those people' becomes 'they' (I've seen this before).
'importing' means one lot of letters goes inside another.
'gold' becomes 'or' ('or' is the heraldic name for gold).
'they' going around 'or' is 'THEORY'.
'made by' acts as a link.
(Other definitions for theory that I've seen before include "Conjectural view" , "Scientific supposition" , "Series of ideas seeking to explain something" , "can provide an explanation" , "Supposition intended to explain observations" .)