Crossword Genius

Item found in Boots by setter, with nothing to hide source of all ... (7)

Ross

I believe the answer is:

hobnail

'item found in boots' is the definition.
(nail in the sole of a boot)

I cannot understand how the rest of the clue works.

(Other definitions for hobnail that I've seen before include "One keeping shoes on" , "Stud for boots" , "Walk over roughly" , "Stud on boot" , "Protection for the sole of a heavy boot" .)

I've seen this clue in The Independent.
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