Mean to declare silver, English (7)
I believe the answer is:
average
'mean' is the definition.
('average' can be a synonym of 'mean')
'declare silver english' is the wordplay.
'declare' becomes 'aver' (averring is a kind of declaring).
'silver' becomes 'ag' (Ag is the chemical symbol for silver).
'english' becomes 'e' (abbreviation).
'aver'+'ag'+'e'='AVERAGE'
'to' is the link.
(Other definitions for average that I've seen before include "Normal in arithmetic way" , "Normal amount" , "Mean, so-so" , "just like any other" , "It's common" .)