Stone in fancy ring men found in river (9)
I believe the answer is:
cairngorm
'stone' is the definition.
(thesaurus)
'fancy ring men found in river' is the wordplay.
'fancy' indicates anagramming the letters.
'men' becomes 'or' (I've seen this in other clues).
'found in' indicates putting letters inside.
'river' becomes 'cam' (I've seen this before).
'ring' anagrammed gives 'irng'.
'irng'+'or'='irngor'
'irngor' placed inside 'cam' is 'CAIRNGORM'.
'in' acts as a link.
(Other definitions for cairngorm that I've seen before include "mountains" , "Stone" .)