A very long time to make a ring (8)
I believe the answer is:
eternity
I believe this is a double definition.
'a very long time' is the first definition.
(I've seen this before)
'a ring' is the second definition.
(I have seen 'A ring' mean 'eternity' so perhaps 'ring' could also mean 'eternity')
'to make' acts as a link.
(Other definitions for eternity that I've seen before include "Evermore" , "Endless period" , "Forever in entirety" , "Infinity" , "Endless duration" .)