It is the extra letters (27)from the normal clues that provide the 5 names in the group.
For example -you asked about 6d - T (C)arboys
Tarboy = shearer & carboy = bottle.
The 9 clues without definition, although entered into the grid as non-words, make sense when readin conjunction with 20a and the actions of the 6th member of the group (Prime Mover)