Opalescent piece of my old china (3)

I believe the answer is:

pal

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

'china' is the definition.
(china plate is Cockney rhyming slang for mate)

'opalescent piece of my old' is the wordplay.
'PAL' is hidden in amongst the letters.
But, I am unsure how the hidden word is indicated.

Can you help me to learn more?

(Other definitions for pal that I've seen before include "Buddy, chum" , "Mate, buddy" , "Brother" , "Bud" , "Mate, informal friend" .)

I've seen this clue in the Evening Standard.

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