Saint with silver deer (4)
I believe the answer is:
stag
'deer' is the definition.
(stag is a kind of deer)
'saint with silver' is the wordplay.
'saint' becomes 'st' (abbreviation).
'with' means one lot of letters go next to another.
'silver' becomes 'Ag' (Ag is the chemical symbol for silver).
'st'+'ag'='STAG'
(Other definitions for stag that I've seen before include "Share speculator" , "Antlered beast" , "Men-only" , "party given by Uncle Sam" , "Male animal" .)