In Eberron: Rising from the Last War, the artificer's Battle Smith subclass grants you a Steel Defender that can use its reaction to give disadvantage on a creature's attack roll.
The Steel Defender feature says:
It can move and use its reaction on its own, [...]
The Steel Defender's statblock lists the following reaction:
Deflect Attack. The defender imposes disadvantage on the attack roll of one creature it can see that is within 5 feet of it, provided the attack roll is against a creature other than the defender.
Does this disadvantage apply to all attacks by the chosen creature, or just to one of its attacks?