Is representative of pietism so troubled about source of evil? (10)

'is representative of' is the definition.
(to epitomise is to be representative of)

'pietism so troubled about source of evil?' is the wordplay.
'troubled' indicates anagramming the letters.
'about' is an insertion indicator.
'source of' says to take the initial letters.
The first letter of 'evil' is 'e'.
'pietism'+'so'='pietismso'
'pietismso' with letters rearranged gives 'epitomiss'.
'epitomiss' placed around 'e' is 'EPITOMISES'.