i play discipline, my oponent reacts with defy, i play abadon into his defy. Both pass prio and chain starts resolving. Abadon sends his defy to his hand, can he defy my disciple before resolution ends?

Yes — he can play Defy from his hand again once Abandon resolves and you pass priority.

When Abandon counters his Defy, that Defy is cleared from the chain and returned to his hand, leaving your Discipline as the only item. A new priority window opens before Discipline resolves: the controller of the newest remaining item (you) gets priority first, but once you pass, priority moves to the next player in turn order — your opponent — and the game is in a Closed State where he may play any legally timed card. Defy is [Reaction], so it's legal, and your Discipline is a valid target.

Same as the classic Defy/Abandon loop (FAQ #9457): the chain resolves one item at a time, not as an unbreakable block (Rule 340.4). Note he pays Defy's cost again — costs are never refunded for a countered card (Rule 425.1.c), and the returned Defy is treated as a new object with a new target choice.