Why no tea is coming (2,3,3)

I believe the answer is:

on the way

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'is coming' is the definition.
(I've seen this in another clue)

'why no tea' is the wordplay.
'why no tea' anagrams to 'ON THE WAY'.
But, I am unsure how this is indicated.

Can you help me to learn more?

(Other definitions for on the way that I've seen before include "In progress" , "En route" , "About to arrive" , "In transit" .)

I've seen this clue in The Irish Independent.

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