Got a response from the Clojure mailing list instructing me on creating an anaphoric macro.
I don't quite understand the name, since according to OED anaphora is:
a. Rhetoric. The repetition of the same word or phrase in several successive clauses. b. Grammar. The use of a word which refers to, or is a substitute for, a preceding word or group of words.
Removed the collection retrieval boilerplate from item with the completed with-collection macro.