Bird with silver in shallow lake (6)
I believe the answer is:
lagoon
'shallow lake' is the definition.
(I've seen this before)
'bird with silver' is the wordplay.
'bird' becomes 'loon' (loon is a kind of bird).
'with' is an insertion indicator.
'silver' becomes 'Ag' (Ag is the chemical symbol for silver).
'loon' enclosing 'ag' is 'LAGOON'.
'in' acts as a link.
(Other definitions for lagoon that I've seen before include "Water protected by a coral reef" , "Shallow salt-water lake" , "Water cut off by coral reefs" , "Coastal lake" , "Shallow seaside lake" .)