Blackmail of former partner wrong? (6)
I believe the answer is:
extort
'blackmail' is the definition.
(I've seen this before)
'former partner wrong?' is the wordplay.
'former partner' becomes 'ex' (an ex-partner).
'wrong?' becomes 'tort' (legal term).
'ex'+'tort'='EXTORT'
'of' is the link.
(Other definitions for extort that I've seen before include "Compel to pay" , "Obtain money with menaces" , "Obtain by force or intimidation" , "Obtain importunately" , "Get by force" .)