Crossword Genius

The bee in one's bonnet? (7)

Ross

I believe the answer is:

initial

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

'in one's bonnet?' is the wordplay.
'one' becomes 'i' (Roman numeral).
'bonnet?' becomes 'tial' (I can't justify this - if you can you should give a lot more credence to this answer).
'in'+'i'+'tial'='INITIAL'

Can you help me to learn more?

(Other definitions for initial that I've seen before include "Introductory" , "Primary" , "shortened version of my name" , "Letter - opening" , "Relating to the beginning" .)

I've seen this clue in The Guardian and The Globe and Mail.
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