Architect of warren leaves Argentina (4)

I believe the answer is:

wren

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'architect' is the definition.
(Christopher Wren, 17th-century architect)

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for wren that I've seen before include "Bird - architect, 1632-1723" , "Bird - former British servicewoman" , "Very small brown songbird (4)" , "Small bird (in the Navy?)" , "Small singer" .)

I've seen this clue in The Mirror.

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