How can I rename a field name with curly braces attached to it e.g. cxy{}
and then compare to a field within a lookup?
You can rename a field using the rename command like this
your base search | rename abc{} as abc
or
your base search | rename abc{}.* as *
However, you can do a lookup without renaming the field like this
your base search | lookup lookupname lookukpfield as abc{} OUTPUT lookupfield