Old Bolshevik pressing Eastern church to show mercy (8)
I believe the answer is:
Here is my best explanation:
'mercy' is the definition.
(lenience is a kind of mercy)
'old bolshevik pressing eastern church' is the wordplay.
I cannot really understand how this works, but
'eastern' could be 'e' and 'e' is located in the answer.
'church' could be 'ce' (abbreviation for Church of England) and 'ce' is present in the answer.
This may be the basis of clue (or it may be nonsense).
'to show' acts as a link.