Crossword Genius

Pressurised exercise useful when breaking up (9,5)

Ross

I believe the answer is:

pneumatic drill

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

'useful when breaking up' is the definition.
I can't judge whether this definition defines the answer.

'pressurised exercise' is the wordplay.
I cannot quite understand how this works, but
'exercise' could be 'drill' (military exercise) and 'drill' is found within the answer.
The remaining letters 'pneumatic' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?

I've seen this clue in The Daily Express.
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