Friend invested in gold rings, originally a dabbler (7)
I believe the answer is:
amateur
'a dabbler' is the definition.
(thesaurus)
'friend invested in gold rings originally' is the wordplay.
'friend' becomes 'mate' (mate is a kind of friend**).
'invested in' is an insertion indicator.
'gold' becomes 'au' ('Au' can be a synonym of 'gold').
'originally' indicates taking the first letters.
The first letter of 'rings' is 'r'.
'mate' placed within 'au' is 'amateu'.
'amateu'+'r'='AMATEUR'
(Other definitions for amateur that I've seen before include "Unpaid (sport)" , "I'm no expert!" , "enthusiast" , "Dabbler" , "Lover" .)