Speculation of people in authority hoarding gold (6)
I believe the answer is:
theory
'speculation' is the definition.
(something theorised or speculated)
'people in authority hoarding gold' is the wordplay.
'people in authority' becomes 'they' (I've seen this in other clues).
'hoarding' means one lot of letters goes inside another.
'gold' becomes 'or' ('or' is the heraldic name for gold).
'they' going around 'or' is 'THEORY'.
'of' is the link.
(Other definitions for theory that I've seen before include "Supposition, hypothesis" , "Assumption" , "Idea for testing" , "The words, as opposed to the practice" , "Proposition, thesis" .)