Kind of iron age bird (6)
I believe the answer is:
pigeon
'bird' is the definition.
(pigeon is a kind of bird)
'kind of iron age' is the wordplay.
'kind of iron' becomes 'pig'.
'age' becomes 'eon' (I've seen this before).
'pig'+'eon'='PIGEON'
(Other definitions for pigeon that I've seen before include "gull" , "Common dove" , "Common bird, wild and domesticated" , "Bird of the dove family" , "Trafalgar Square bird?" .)