3 down: The rest of Barcelona change top for party (6)
This took a while, but the semantic switch makes for a nice clue indeed. Party = fiesta so that change top for party = siesta = the rest of Barcelona.
6 down: Within a schedule, skipper shows respect, perhaps, is in reach (10)
Ridiculously clever clue. Here, skipper = captain, skipper shows respect = tain (one doffs one’s cap to show respect) and schedule = table so that within a schedule, skipper shows respect, perhaps = attainable = is in reach.
7 down: Residents liable to be punished by thematic overindulgence? (6)
As mentioned in the report, RC conjured up livers as a synonym for residents so that residents = livers = liable to be punished by thematic overindulgence to reveal the theme.
22 across: How this themed group is made in group-speak (6)
Nice sounds-like clue, with group = brood so that group-speak = brewed = how this themed group is made.