Piece of information obtained from US lawyer by corporation (5)
I believe the answer is:
datum
'piece of information' is the definition.
(singular form of 'data')
'us lawyer by corporation' is the wordplay.
'us lawyer' becomes 'DA' (abbreviation for District Attorney).
'by' means one lot of letters go next to another.
'corporation' becomes 'tum' ('corporation' is a humorous term for stomach fat).
'da'+'tum'='DATUM'
'obtained from' acts as a link.
(Other definitions for datum that I've seen before include "Premiss, thing taken for granted" , "Given item" , "Single piece of information" , "Something given" , "One item of information" .)