Era of silver finally gone (3)
I believe the answer is:
age
'era' is the definition.
(I've seen this before)
'silver finally gone' is the wordplay.
'silver' becomes 'Ag' (Ag is the chemical symbol for silver).
'finally' says to take the final letters.
The final letter of 'gone' is 'e'.
'ag'+'e'='AGE'
'of' acts as a link.
(Other definitions for age that I've seen before include "Period of time" , "Get older" , "Years lived so far" , "Years since birth" , "Period of history" .)