Bootleg film content on a Roman cardinal (7)

I believe the answer is:

illegal

I'm a little stuck... Click here to teach me more about this clue!

'bootleg' is the definition.
(similar in meaning)

'film content on a roman cardinal' is the wordplay.
'content' means to look at the middle letters.
'on' becomes 'leg' (cricket term).
'roman cardinal' becomes 'l' (similar in meaning. I am not sure about the 'roman' bit.).
The middle letters of 'film' are 'il'.
'il'+'leg'+'a'+'l'='ILLEGAL'

Can you help me to learn more?

(Other definitions for illegal that I've seen before include "Criminal, illicit" , "Against the rules" , "Forbidden" , "Ignoring certain acts" , "Not allowed" .)

I've seen this clue in the Sydney Morning Herald.

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