An injection, yes, with British capital (3)

I believe the answer is:

jab

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'an injection' is the definition.
(I've seen this before)

'yes with british capital' is the wordplay.
'yes with' becomes 'ja' (I can't explain this - if you can you should give a lot more credence to this answer).
'capital' says to take the initial letters.
The first letter of 'british' is 'b'.
'ja'+'b'='JAB'

Can you help me to learn more?

(Other definitions for jab that I've seen before include "Injection" , "A short stiff punch" , "Poke roughly or inject" , "Prod" , "Short stiff blow or thrust" .)

I've seen this clue in the Evening Standard.

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