Detective who leaves sticky footprints behind him? (7)

I believe the answer is:

gumshoe

I'm a little stuck... Click here to teach me more about this clue!

'detective' is the definition.
(gumshoe is a kind of detective)

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for gumshoe that I've seen before include "American detective (informal)" , "Foreign investigator" , "US detective (informal)" , "Possible US version of Morse" , "Detective (US colloq.)" .)

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