Crossword Genius

The original cause of disloyalty (7)

Ross

I believe the answer is:

treason

'disloyalty' is the definition.
(treason is a kind of disloyalty)

'the original cause' is the wordplay.
'original' suggests taking the first letters.
'cause' becomes 'reason' (I've seen this before).
The initial letter of 'the' is 't'.
't'+'reason'='TREASON'

'of' is the link.

(Other definitions for treason that I've seen before include "Disloyalty (to one's country)" , "Mutiny" , "Offence against state" , "LEse-majestE" , "Betrayal of the state" .)

I've seen this clue in the Sydney Morning Herald.
Want a hint initially instead of a full solution? Install my app