Reach an insurmountable obstacle that a thick bar will break (3,1,5,4)

I believe the answer is:

hit a brick wall

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'reach an insurmountable obstacle that a thick bar will break' is the definition.
I know nothing about this answer so I can't tell whether this works.

'reach an insurmountable obstacle that a thick bar will break' is the wordplay.
'a thick bar will' anagrams to 'HIT A BRICK WALL'.
Though, I am not sure how the anagram is indicated.

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I've seen this clue in the Sydney Morning Herald.

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