Film takes against leading supporter of the royals (10)
I believe the answer is:
monarchist
'supporter of the royals' is the definition.
'monarchist' can be an answer for 'supporter' (I have seen 'Royal supporter' mean 'monarchist' so perhaps 'supporter' could also mean 'monarchist'). I'm not certain of the 'of the royals' bit.
'film takes against leading' is the wordplay.
I cannot really understand how this works, but
'film' could be 'm' (1931 Fritz Lang film) and 'm' is found within the answer.
'takes' could be 'is' (being is a kind of taking) and 'is' is found in the answer.
'against' could be 'on' (I've seen this in other clues) and 'on' is found within the answer.
'leading' could be 'arch' (e.g. in arch-enemy) and 'arch' is located in the answer.
A single letter 't' remains which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for monarchist that I've seen before include "Royal supporter" , "Supporter of hereditary rule" .)