Tread on sticker (5)
I believe the answer is:
stamp
This clue is a double definition.
'tread' is the first definition.
(thesaurus)
'sticker' is the second definition.
(I've seen this in another clue)
'on' acts as a link.
(Other definitions for stamp that I've seen before include "Impress (a pattern)" , "Kind" , "What to put on 7 before putting in 15" , "Impress with a mark" , "Bang foot down; (house sale) duty" .)