A crack about Tory leader being in the wrong (2,5)
I believe the answer is:
at fault
'in the wrong' is the definition.
(I've seen this before)
'a crack about tory leader' is the wordplay.
'crack' becomes 'fault' (fault is a kind of crack**).
'about' says to put letters next to each other.
'tory leader' becomes 't' (I've seen this in other clues).
'fault' put after 't' is 'tfault'.
'a'+'tfault'='AT FAULT'
'being' acts as a link.
(Other definitions for at fault that I've seen before include "In the wrong" , "Guilty" , "To blame, responsible for mistake" , "Rightly taking the blame" , "To blame, culpable" .)