A bit of calm, say (5)
I believe the answer is:
piece
'a bit of' is the definition.
(I've seen this before)
'calm say' is the wordplay.
'calm' becomes 'peace' (peaceful situation).
'say' indicates a 'sounds like' (homophone) clue.
'peace' is a homophone of 'PIECE'.
(Other definitions for piece that I've seen before include "Part - portion" , "Chessman; portion" , "Chessman - part - firearm" , "A bit of something" , "Portion, coin, item" .)