Piece of information a corporation's given to board at last (5)
I believe the answer is:
datum
'piece of information' is the definition.
(I've seen this before)
'a corporation's given to board at last' is the wordplay.
'corporation' becomes 'tum' ('corporation' can humorously mean belly fat).
'given to' says to put letters next to each other.
'at last' suggests the final letters.
The last letter of 'board' is 'd'.
'a'+'tum'='atum'
'atum' after 'd' is 'DATUM'.
(Other definitions for datum that I've seen before include "Minimal information" , "Given piece of information" , "Premiss, thing taken for granted" , "Single piece of information" , "Given point or position" .)