Get Phi calm, unusually calm (10)
I believe the answer is:
phlegmatic
'calm' is the definition.
(I've seen this before)
'get phi calm unusually' is the wordplay.
'unusually' is an anagram indicator.
'get'+'phi'+'calm'='getphicalm'
'getphicalm' anagrammed gives 'PHLEGMATIC'.
(Other definitions for phlegmatic that I've seen before include "Calm; philosophical" , "Unexcitable" , "dull and lifeless" , "Unemotional" , "cool" .)