One bird bit another (7)

I believe the answer is:

bittern

I'm a little stuck... Click here to teach me more about this clue!

'one bird' is the definition.
(bittern is a kind of bird)

'bit another' is the wordplay.
'another' becomes 'tern' (I can't explain this - if you can you should believe this answer much more).
'bit'+'tern'='BITTERN'

Can you help me to learn more?

(Other definitions for bittern that I've seen before include "large wader" , "Source of boom" , "found hidden in reed-beds" , "Bird that booms" , "flier" .)

I've seen this clue in the Evening Standard.

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