Snail mail need (5)
I believe the answer is:
stamp
'snail mail need' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for stamp that I've seen before include "Evidence of payment of postage duty" , "Mark of approval" , "put one's foot down hard" , "Philatelist's item" , "Impress; postage sticker" .)