Couple possessing too much information about songbirds (7)

I believe the answer is:

titmice

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

'songbirds' is the definition.
(I have seen 'Small songbirds ' mean 'titmice' so perhaps 'songbirds' could also mean 'titmice')

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for titmice that I've seen before include "Little singers" , "little birds" , "Small birds" , "Small, active songbirds" .)

I've seen this clue in The Telegraph.

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