Raincoat made of rubberised fabric by an Austrian physicist reportedly (3)

I believe the answer is:

mac

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'raincoat' is the definition.
(mac is a kind of raincoat)

I cannot understand how the remainder of the clue works.

(Other definitions for mac that I've seen before include "PC" , "It may help you keep dry" , "Raincoat (colloq.)" , "one used in shower?" , "Waterproof raincoat, in short" .)

I've seen this clue in The Hindu.

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