Detective sticks on an implement (7)
I believe the answer is:
gumshoe
'detective' is the definition.
(I know that gumshoe is a type of detective)
'sticks on an implement' is the wordplay.
'sticks' becomes 'gums'.
'on' is a charade indicator (letters next to each other) (in a down clue, letters appear on others).
'an implement' becomes 'hoe' (hoe is a kind of implement).
'gums'+'hoe'='GUMSHOE'
(Other definitions for gumshoe that I've seen before include "Foreign investigator" , "Detective (US colloq.)" , "Galosh - sleuth" , "American detective (informal)" , "footwear" .)