Failed to keep calm to be purified (9)
I believe the answer is:
distilled
'purified' is the definition.
('distill' can be a synonym of 'purify')
'failed to keep calm' is the wordplay.
'failed' becomes 'died' ('die' can be a synonym of 'fail').
'to keep' is an insertion indicator.
'calm' becomes 'still' ('still' can be a synonym of 'calm'**).
'died' placed around 'still' is 'DISTILLED'.
'to be' is the link.
(Other definitions for distilled that I've seen before include "produced whisky" , "Brewed" .)