Opening broken relic's hollow cavities (10)

I believe the answer is:

ventricles

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

'hollow cavities' is the definition.
'ventricles' can be an answer for 'cavities' (ventricle is a kind of cavity). I'm not sure about the 'hollow' bit.

'opening broken relic's' is the wordplay.
'opening' becomes 'vent' (vent is a kind of opening).
'broken' indicates an anagram.
'relics' is an anagram of 'ricles'.
'vent'+'ricles'='VENTRICLES'

Can you help me to learn more?

(Another definition for ventricles that I've seen is " Chambers".)

I've seen this clue in The Independent.

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