Stupid Sherlock Holmes never was (8)

I believe the answer is:

clueless

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'stupid' is the definition.
(I've seen this before)

I cannot understand how the rest of the clue works.

(Other definitions for clueless that I've seen before include "Without any understanding" , "Ignorant (informal)" , "Totally uninformed about what's going on" , "how I started this puzzle!" , "such a crossword can't be solved!" .)

I've seen this clue in the Evening Standard.

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