Question regarding querying an association with Compass.

Hello,

I'm having troubles using compass to query an association.  I don't have control over the database schema, so I'm forced to adhere to this domain representation:

class Genre {
   
    static searchable = [only:['id']]
    Integer id

    String name
    Set entries = new LinkedHashSet()
    //etc.
}

class Entry {
    static searchable = [only: ['title', 'content', 'category']]
    Genre category
    String title
    String content
    //etc.
}

I'd like to be able to perform full-text queries on Entries such that I can restrict the results to a category.
I've searched around quite a bit, and I'm still stumped.  
   
I've tried all the variations on

def searchResult = Entry.search {
    queryString("query string")
    term("category.id", 1)
}

etc.

I'd appreciate it if someone would point out where I'm going wrong.

Thanks!

Joe