Opening provided to infiltrate gold reserve (7)
I believe the answer is:
orifice
'opening' is the definition.
(synonyms)
'provided to infiltrate gold reserve' is the wordplay.
'provided' becomes 'if' (eg 'provided it's sunny' means 'if it's sunny').
'to infiltrate' is an insertion indicator.
'gold' becomes 'or' ('or' is the heraldic name for gold).
'reserve' becomes 'ice ' (both can mean aloofness).
'or'+'ice'='orice'
'if' inserted inside 'orice' is 'ORIFICE'.
(Other definitions for orifice that I've seen before include "Vent" , "Bodily hole" , "For CIE, I look for an opening" , "Mouth-like opening" , "Hole in the head, perhaps?" .)