Calm grew outside European Parliament (6)
I believe the answer is:
repose
'calm' is the definition.
(I know that repose is a type of calm)
'grew outside european parliament' is the wordplay.
'grew' becomes 'rose' (rise can mean to grow or increase).
'outside' means one lot of letters goes inside another.
'european parliament' becomes 'EP' (abbreviation).
'rose' going around 'ep' is 'REPOSE'.
(Other definitions for repose that I've seen before include "Rest - tranquillity" , "place" , "Relaxation" , "calm" , "peace" .)