narrow vein crossword clue

 Here is a cryptic crossword clue for the word "narrow vein":

Stream that runs through a mountain (6): STRAIN

The wordplay clue in this cryptic crossword clue is the word "stream." A stream is a narrow body of water that runs through a mountain. In this clue, the word "stream" is being used as a homophone for the word "strain." A strain is a narrow vein.

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