Crossword Genius

Each one welcomed to a pizza pie celebration (6)

Ross

I believe the answer is:

apiece

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

'each one' is the definition.
(I've seen this before)

'welcomed to a pizza pie celebration' is the wordplay.
'APIECE' is hidden in amongst the letters.
But, I am uncertain how this is indicated.

Can you help me to learn more?

(Other definitions for apiece that I've seen before include "For or by each one of group" , "for everyone" , "A head" , "Per person" .)

I've seen this clue in The Guardian.
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