Ring for a long time (8)
I believe the answer is:
eternity
This clue is a triple definition!
'ring' is the first definition.
(eternity ring is a type of ring)
'for' acts as a link.
'a long' is the second definition.
(thesaurus)
'time' is the third definition.
(I know that eternity is a type of time)
(Other definitions for eternity that I've seen before include "Evermore" , "An extremely long time" , "Entirety (anag.)" , "Forever and ever" , "destination of film?" .)