Sent message with papers: note enclosed (5)
I believe the answer is:
wired
'sent message' is the definition.
(wire can mean to send a telegram)
'with papers note enclosed' is the wordplay.
'with' becomes 'w' (abbreviation).
'papers' becomes 'ID' (identification papers).
'note' becomes 're' (as in do-re-mi).
'enclosed' is an insertion indicator.
'id' going around 're' is 'ired'.
'w'+'ired'='WIRED'
(Other definitions for wired that I've seen before include "Connected to an electricity supply" , "Using cables; tense, edgy" , "Equipped for electrical connection" , "Sent a telegram" , "Equipped for electricity" .)