Opening provided to invest in gold and diamonds (7)
I believe the answer is:
orifice
'opening' is the definition.
('orifice' can be a synonym of 'opening')
'provided to invest in gold and diamonds' is the wordplay.
'provided' becomes 'if'.
'to invest in' is an insertion indicator.
'gold' becomes 'or' ('or' is the heraldic name for gold).
'and' means one lot of letters go next to another.
'diamonds' becomes 'ice' (I've seen this before).
'or'+'ice'='orice'
'if' going within 'orice' is 'ORIFICE'.
(Other definitions for orifice that I've seen before include "Hole, opening" , "Space" , "provided by gold and diamonds" , "Bodily opening, mouth of cavity" , "For CIE, I look for an opening" .)