If a character is grappling a struggling opponent, and a second opponent attacks the character, would the DM rule that the distraction of dealing with the grappled opponent causes opponent number 2 to have Advantage on its attack?
I suppose it might depend on the nature of the Grapple. Merely grabbing an opponent by the wrist to impede his slingshot might leave you alert and ready to parry or dodge, but a more violent tussle, involving a grab with both arms would, I presume, leave you wide open for a whack from behind and thus at a Disadvantage versus a second opponent.
Even if you have followed up with a move to leave your grappled opponent Prone, I imagine that you are now kneeling, crouching or otherwise distorting your fighting stance in such a way (at least I cannot imagine that grappling a prone opponent can be done standing up) as to give a second opponent the Advantage.
I don't see anything in the Rules (I have Essentials Kit Rulebook) covering this.
The rules regarding grappled condition only speak of the relationship between grappler and victim. I am asking about the relationship between grappler and a third participant standing adjacent. Perhaps there is an applicable general rule somewhere that covers circumstances in which the character might conceivably be distracted (by which I mean Distracted as a Condition (in the manner of Blinded, Deafened etc.) which allows attack rolls with Advantage)?
Furthermore, one use of the Help action is to "distract the target" leading to the next attack roll against the target being made with advantage. So the target being distracted may be in and of itself the trigger for an Advantage roll. I am asking if being engrossed in a grapple might be considered a distraction for the purposes of Advantage. Seems to me the Rules might cover this somewhere.