Piece of information nowadays withdrawn by corporation (5)
I believe the answer is:
datum
'piece of information' is the definition.
(singular form of 'data')
'nowadays withdrawn by corporation' is the wordplay.
'nowadays' becomes 'AD' (AD, Anno Domini, as opposed to BC, Before Christ).
'withdrawn' says the letters should be written backwards.
'by' says to put letters next to each other.
'corporation' becomes 'tum' ('corporation' is a humorous term for stomach fat).
'ad' back-to-front is 'da'.
'da'+'tum'='DATUM'
(Other definitions for datum that I've seen before include "Single piece of information" , "Given item" , "Little bit of information" , "Something given" , "Fixed starting point for measurements" .)