Worshipping establishment, peculiar old leader (9)
I believe the answer is:
churchill
'old leader' is the definition.
(I've seen this before)
'worshipping establishment peculiar' is the wordplay.
'worshipping establishment' becomes 'church' (place of worship).
'peculiar' becomes 'ill'.
'church'+'ill'='CHURCHILL'
(Other definitions for churchill that I've seen before include "13 [THIRD REICH] 's nemesis" , "Old leader" , "He offered the British people "nothing but blood, toil, tears and sweat"" , "PM and Nobel prize winner" , "Former statesman" .)