Anti-PC rioting that is irresistible to Tom (6)
I believe the answer is:
catnip
'that is irresistible to tom' is the definition.
(tom can mean a male cat)
'anti-pc rioting' is the wordplay.
'rioting' is an anagram indicator.
'anti'+'pc'='antipc'
'antipc' anagrammed gives 'CATNIP'.
(Other definitions for catnip that I've seen before include "Tin cap (anag.)" , "Plant with scented leaves which felines like" , "Plant favoured by felines" , "flower" , "Puss would like that" .)