It all depends on what you meant by "tightly related functionality". There can be 2 interpretations:
These set of functions implement a particular component/sub-system of the system. Example: Logging, Authentication etc. In this case you will probably use a clojure namespace (AKA module) to group the related functions rather than using a hash map.
These set of functions work together on some data structure or type or object etc. In this case you will use Protocol based approach, which allows ad-hoc polymorphism such that new types can also provide this set of functionality. Example: Any interface kind of thing: Sortable, Printable etc.