I use Ekko to play Clocktower Guardian with discount. He dies at the end of the turn and I Play houndwards with two power. Then there is a time warp on top of my deck. Do I get an extra turn?

It depends on your Power. Clocktower Guardian's Deathknell only ignores the banished card's Energy cost — you still have to pay Time Warp's 4 Power (same rule as FAQ #12960 for this exact card). If you've only got 2 Power left, you can't play it, it stays banished, and you get no extra turn.

If you can pay the 4 Power, then yes — playing it in the end-of-turn window doesn't waste it. The "Kill me at end of turn" kill resolves in the Ending Step, before your rune pool empties (Rule 317.2), so the Power is still there, and the extra turn is inserted into the turn queue directly after the current turn (Rule 735), meaning you take it before the next player's turn. Time Warp then banishes itself as normal.

One caveat on the setup: only the card that is actually on top when the Guardian dies gets banished, so make sure the Time Warp is on top at that moment — I couldn't identify a card called "Houndwards," so if that's something that shuffles/recycles your top card, it matters which order it resolved in.