Type and prepare to post (5)
I believe the answer is:
stamp
'type' is the definition.
(thesaurus)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for stamp that I've seen before include "Evidence of payment of postage duty" , "contributions?" , "Impress (a pattern)" , "Imprint, brand" , "Bring foot down hard" .)