Dishonesty getting last chairman sacked (12)
I believe the answer is:
charlatanism
'dishonesty' is the definition.
(charlatanism is a kind of dishonesty)
'getting last chairman sacked' is the wordplay.
'getting' means one lot of letters go next to another.
'sacked' is an anagram indicator.
'last' put after 'chairman' is 'chairmanlast'.
'chairmanlast' with letters rearranged gives 'CHARLATANISM'.
(Other definitions for charlatanism that I've seen before include "Quacking" , "Animal starch (anag) - quackery" .)