Ruler supporting a mass and religious instruction in Indian city (8)
I believe the answer is:
amritsar
'indian city' is the definition.
(I've seen this before)
'ruler supporting a mass and religious instruction' is the wordplay.
'ruler' becomes 'tsar' (historical term for Russian king).
'supporting' means one lot of letters go next to another (in a down clue, some letters go below others).
'mass' becomes 'm' (symbol used in Physics e.g. f=ma).
'and' is a charade indicator (letters next to each other).
'religious instruction' becomes 'RI' (abbreviation).
'a'+'m'+'ri'='amri'
'tsar' after 'amri' is 'AMRITSAR'.
'in' acts as a link.
(Other definitions for amritsar that I've seen before include "Punjab city, centre of Sikh faith" , "Eastern city" , "Asian city" , "Holy city of Sikhism" , "Indian city, centre of the Sikh faith" .)