Conjecture made by those people importing gold (6)
I believe the answer is:
Here is my best explanation:
'conjecture' is the definition.
(I've seen this before)
'those people importing gold' is the subsidiary indication.
'those people' becomes 'they' (I've seen this in other clues).
'importing' is an insertion indicator.
'gold' becomes 'or'.
'they' enclosing 'or' is 'theory'.
'made by' is the link.
(Other definitions for theory that I've seen before include "Hypothesis - doctrine", "Proposition, thesis", "Hypothetical reasoning", "Series of ideas seeking to explain something", "speculative view", "A conjecture to explain something", "Ideal situation", "Conjectural view", "Suggested explanation" and "Scientific supposition".)