Stamps (7)
'stamps' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for postage that I've seen before include "Amount paid to mail" , "Money charged for delivery" , "Charge for 23 Acrosses" , "It could be first-class" , "Cost of corresponding" .)
(Other definitions for treads that I've seen before include "Sets the foot down." , "Steps, walks" , "Stared at tyre surfaces" , "mates" , "Puts the foot down" .)