Clockwork Droid — ruling 1

You can't exert a creature unless an effect allows you to do so. Similar effects that "tap and freeze" a creature don't exert that creature.

Clockwork Droid — ruling 2

If an exerted creature is already untapped during your next untap step (most likely because it had vigilance or an effect untapped it), exert's effect preventing it from untapping expires without having done anything.

Clockwork Droid — ruling 3

If you gain control of another player's creature until end of turn and exert it, and then that player regains control of it, it will untap during that player's untap step.

Clockwork Droid — ruling 4

You may exert Clockwork Droid only as you attack with it. You can't do so later in combat, and creatures put onto the battlefield attacking can't be exerted. The ability that triggers on exerting it will resolve before blockers are declared.

Clockwork Droid : règles, fonctionnement et interactions (MTG)

Clockwork Droid is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

You may exert this creature as it attacks. When you do, it can't be blocked this turn and you scry 1. (An exerted creature won't untap during your next untap step. To scry 1, look at the top card of your library. You may put that card on the bottom.)

How it works : Clockwork Droid

Original English text — Wizards of the Coast / Scryfall

#1October 13, 2023· Wizards of the Coast
You can't exert a creature unless an effect allows you to do so. Similar effects that "tap and freeze" a creature don't exert that creature.
No other card is named in this ruling.
#2October 13, 2023· Wizards of the Coast
If an exerted creature is already untapped during your next untap step (most likely because it had vigilance or an effect untapped it), exert's effect preventing it from untapping expires without having done anything.
No other card is named in this ruling.
#3October 13, 2023· Wizards of the Coast
If you gain control of another player's creature until end of turn and exert it, and then that player regains control of it, it will untap during that player's untap step.
No other card is named in this ruling.
#4October 13, 2023· Wizards of the Coast
You may exert Clockwork Droid only as you attack with it. You can't do so later in combat, and creatures put onto the battlefield attacking can't be exerted. The ability that triggers on exerting it will resolve before blockers are declared.
No other card is named in this ruling.