Tread on a sticker (5)
I believe the answer is:
stamp
I believe this is a double definition.
'tread' is the first definition.
(thesaurus)
'sticker' is the second definition.
(I've seen this in another clue)
'on a' is the link.
(Other definitions for stamp that I've seen before include "Hallmark" , "Tread heavily (on an envelope?)" , "Use a die; character" , "Trample" , "Mark of approval" .)