Endless lunch as tea? It's indecent! (8)

I believe the answer is:

unchaste

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'it's indecent' is the definition.
(thesaurus)

'endless lunch as tea?' is the wordplay.
'UNCHASTE' is hidden in amongst the letters.
But, I'm unsure how this is indicated.

Can you help me to learn more?

(Other definitions for unchaste that I've seen before include "Sexually immodest" , "loose" , "No longer pure" , "Dissolute" , "fallen" .)

I've seen this clue in The Telegraph.

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