Crossword Genius

Comprehensive where castle may have gone? (6-3-5)

Ross

I believe the answer is:

across-the-board

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'comprehensive' is the definition.
(thesaurus)

I cannot understand how the remainder of the clue works.

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(Other definitions for across-the-board that I've seen before include "generally" , "General" , "How men may move" .)

I've seen this clue in The Telegraph.
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