Chap who finally encountered Queen in Tube under some pressure? (9)

I believe the answer is:

manometer

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'tube under some pressure?' is the definition.
(tube of liquid measuring pressure)

'chap who finally encountered queen in' is the wordplay.
'chap' becomes 'Man' (chap can mean a man).
'finally' says to take the final letters.
'encountered queen in' becomes 'meter' (I can't explain this - if you can you should believe this answer much more).
The final letter of 'who' is 'o'.
'man'+'o'+'meter'='MANOMETER'

Can you help me to learn more?

(Another definition for manometer that I've seen is " Simple pressure gauge".)

I've seen this clue in The Times.

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