Crossword Genius

Platform which made bluebird cross? (7)

Ross

I believe the answer is:

twitter

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

This might be a double definition.

'platform' is the first definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.

'made bluebird cross?' is the second definition.
The answer and definition can be both related to natural events as well as being singular nouns.
Perhaps there's an association between them I don't understand?

'which' acts as a link.

Can you help me to learn more?

(Other definitions for twitter that I've seen before include "Chirpy social medium" , "Electronic social network" , "Talk excitedly" , "Sound made by bird" , "Bird's sound; trivial talk" .)

I've seen this clue in The Independent.
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