Commercial mail centre undergoing renovation (10)

I believe the answer is:

mercantile

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'commercial' is the definition.
(similar in meaning)

'mail centre undergoing renovation' is the wordplay.
'mail centre' anagrams to 'MERCANTILE'.
However, I'm not clear how the anagram is indicated.

Can you help me to learn more?

(Other definitions for mercantile that I've seen before include "Relating to trade or commerce" , "Commercial" , "related to business" , "concerning trade" , "Dealing with trade" .)

I've seen this clue in The Telegraph.

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