See silver found in island excavation (7)
I believe the answer is:
imagine
'see' is the definition.
(I know that see is a kind of imagine)
'silver found in island excavation' is the wordplay.
'silver' becomes 'Ag' (Ag is the chemical symbol for silver).
'found in' means one lot of letters goes inside another.
'island' becomes 'i' (geographical abbreviation).
'excavation' becomes 'mine' (mine is a kind of excavation).
'i'+'mine'='imine'
'ag' put into 'imine' is 'IMAGINE'.
(Other definitions for imagine that I've seen before include "Suppose; conceive" , "Believe to be so, suppose" , "Conjure up in mind,fancy" , "John Lennon hit" , "A Gemini? (anag)" .)