It's just retribution (7)
I believe the answer is:
nemesis
'retribution' is the definition.
(spirit of retribution in Greek mythology)
'it's' is the wordplay.
I cannot quite understand how this works, but
'it's' could be 'es' ('e' can mean 'electronic' which is similar to 'IT') and 'es' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
'just' acts as a link.
Can you help me to learn more?
(Other definitions for nemesis that I've seen before include "causes downfall" , "enemy" , "Nee Miss (anag.)" , "Retributive justice" , "curse" .)