Savoir faire includes the writer being understood (5)
I believe the answer is:
tacit
'being understood' is the definition.
(I've seen this before)
'savoir faire includes the writer' is the wordplay.
'savoir faire' becomes 'tact' (I've seen this in another clue).
'includes' means one lot of letters goes inside another.
'the writer' becomes 'I' (the person who is writing these clues).
'tact' going around 'i' is 'TACIT'.
(Other definitions for tacit that I've seen before include "Unspoken but implied" , "Implied without being said" , "Implied without being stated" , "Implied, unstated" , "Unvoiced" .)