It's hard hit when ironworkers strike (5)

I believe the answer is:

anvil

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'it's hard' is the definition.
(I know this)

I don't understand how the remainder of the clue works.

(Other definitions for anvil that I've seen before include "A blacksmith's iron block" , "Metalworker's block" , "Smithy's block" , "Forging block" , "Block for hammering" .)

I've seen this clue in The Globe and Mail.

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