A royal descendant in criminal act (5)

I believe the answer is:

arson

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

'criminal act' is the definition.
'arson' can be an answer for 'act' (arson is a kind of act). I am not sure about the 'criminal' bit.

'a royal descendant' is the wordplay.
'royal' becomes 'r' (abbreviation).
'descendant' becomes 'son' (I've seen this before).
'a'+'r'+'son'='ARSON'

'in' is the link.

Can you help me to learn more?

(Other definitions for arson that I've seen before include "Illegally firing" , "Incendiarism" , "Felonious burning of property" , "Criminal burning of property" , "burning problem" .)

I've seen this clue in The Hindu.

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