Property crime (5)
'property crime' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for arson that I've seen before include "Incendiary act" , "Crime of fire-setting (5)" , "serious offence" , "Fire-raiser's crime" , "Iniquitous behaviour" .)
(Other definitions for theft that I've seen before include "Act of larceny" , "Illegal act of taking" , "Act of stealing" , "Pilferage" , "Dishonest taking of others' property" .)