Blackmail former lover not bothered about riot developing (9)
I believe the answer is:
Here is my best explanation:
'blackmail' is the definition.
(I've seen this before)
'former lover not bothered about riot developing' is the subsidiary indication.
'former lover' becomes 'ex'.
'bothered' is an anagram indicator.
'about' is an insertion indicator.
'developing' is an anagram indicator.
'not' is an anagram of 'ton'.
'riot' anagrammed gives 'rtio'.
'ton' going around 'rtio' is 'tortion'.
(Other definitions for extortion that I've seen before include "Blackmail", "The obtaining of money by force or threat" and "Extraction of money with menaces".)