Does drop here mean turns? I came across it reading servants reviews usually with 5 or 6 drop farming phrase
Usually, the expression is “6-slot.” Just refers to the number of Craft Essence slots that can be used for event bonuses, bond gain, etc.
E.g. If you have a 5-slot team, that might mean that you need to put a starting NP charge CE like scope on your main attacker, but the other CE slots can be anything. The assumption is that this is the condition for clearing the quest in the minimum number of turns, typically three.