Merciful Russian revolutionary receiving English on time (7)
I believe the answer is:
lenient
'merciful' is the definition.
('lenient' can be a synonym of 'merciful')
'russian revolutionary receiving english on time' is the wordplay.
'russian revolutionary' becomes 'lenin' (I've seen this before).
'receiving' indicates putting letters inside.
'english' becomes 'e' (abbreviation).
'on' is a charade indicator (letters next to each other).
'time' becomes 't'.
'lenin' going around 'e' is 'lenien'.
'lenien'+'t'='LENIENT'
(Other definitions for lenient that I've seen before include "Tolerant, rather than strict" , "Easy, soft" , "Tolerant, merciful" , "Forgiving, soft" , "'Indulgent, easy (7)'" .)