Bird's name for old coin (5)
I believe the answer is:
crown
'old coin' is the definition.
(I've seen this before)
'bird's name' is the wordplay.
'bird' becomes 'crow' (crow is a kind of bird).
'name' becomes 'n' (common abbreviation e.g. on forms).
'crow'+'n'='CROWN'
'for' acts as a link.
(Other definitions for crown that I've seen before include "Old coin; top of tree" , "sporting award" , "Headdress, coin" , "Diadem" , "Highest part; coin" .)