Being caught outright, is tough (4)

I believe the answer is:

hard

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'is tough' is the definition.
(synonyms)

I don't understand the rest of the clue.

(Other definitions for hard that I've seen before include "Solid, firm, rigid" , "Solid; tough" , "Difficult; rigid" , "Newspaper's sure" , "Tough; rigid" .)

I've seen this clue in the Evening Standard.

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