Great, maybe, but still a small bird (3)

I believe the answer is:

tit

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'small bird' is the definition.
(I've seen this before)

I don't understand how the remainder of the clue works.

(Other definitions for tit that I've seen before include "Boob made backing" , "18's [BIRD]" , "Small bird that lives off insects" , "Small songbird" , "useless horse, or not?" .)

I've seen this clue in the Evening Standard.

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