If I had a map with :billing-address and :shipping-address keys whose associated values were expected to be valid against the same ::address spec, could I express that in spec/keys directly - i.e. without creating intermediary ::billing-address and ::shipping-address specs? Also not sure if (spec/def ::billing-address ::address) or something like it, is an option?

you would need to do the latter, which is an option

it's often convenient to have both structural specs (like address) and named attributes that refer to those

Ok fab - thanks @alexmiller Probably seen that in code many times but not really thought about it much. Trying to build a API data dictionary at work that promotes specifying attributes over HTTP request/responses bodies (to avoid the repetition that brings.) Looks like I will need to list these named specs in the dictionary as well as the attributes themselves.