It's seed, but a songbird has an ear for it! (5)
I believe the answer is:
wheat
'it' is the definition.
The definition suggests a singular noun which matches the answer.
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for wheat that I've seen before include "Cereal for bread/pasta" , "Cereal crop" , "A cereal, to be separated from chaff" , "food plant" , "Annual grass with light brown grains" .)