Puts in the box or on the board (5)
I believe the answer is:
posts
'puts in the box' is the definition.
The definition and answer can be both acts as well as being plural nouns.
Perhaps there's an association between them I don't understand?
'on the board' is the wordplay.
'on' indicates putting letters inside (as in clothing 'on' a person).
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
'board' becomes 'poss' (I can't justify this - if you can you should give a lot more credence to this answer).
't' inserted within 'poss' is 'POSTS'.
'or' acts as a link.
Can you help me to learn more?
(Other definitions for posts that I've seen before include "Mails the uprights?" , "Jobs and poles" , "Stakes" , "Is dispatching" , "Sends by mail" .)