How do I get the most frequent word in a Map and it's corresponding frequency of occurrence using Java 8 streams?

I have a class IndexEntry which looks like this:

public class IndexEntry implements Comparable<IndexEntry>
{
    private String word;
    private int frequency;
    private int documentId;
    ...
    //Simple getters for all properties
    public int getFrequency()
    {
        return frequency;
    }
    ...
}

I am storing objects of this class in a Guava SortedSetMultimap (which allows for multiple values per key) where I am mapping a String word to some IndexEntrys. Behind the scenes, it maps each word to a SortedSet<IndexEntry>.

I am trying to implement a sort of indexed structure of words to documents and their occurrence frequencies inside the documents.

I know how to get the count of the most common word, but I can't seem to get the word itself.

Here is what I have to get the count of the most common term, where entries is the SortedSetMultimap, along with helper methods:

public int mostFrequentWordFrequency()
{
    return entries
            .keySet()
            .stream()
            .map(this::totalFrequencyOfWord)
            .max(Comparator.naturalOrder()).orElse(0);
}

public int totalFrequencyOfWord(String word)
{
    return getEntriesOfWord(word)
            .stream()
            .mapToInt(IndexEntry::getFrequency)
            .sum();
}

public SortedSet<IndexEntry> getEntriesOfWord(String word)
{
    return entries.get(word);
}

I am trying to learn Java 8 features because they seem really useful. However, I can't seem to get the stream working the way I want. I want to be able to have both the word and it's frequency at the end of the stream, but barring that, if I have the word, I can very easily get the total occurrences of that word.

Currently, I keep ending up with a Stream<SortedSet<IndexEntry>>, which I can't do anything with. I don't know how to get the most frequent word without the frequencies, but if I have the frequency, I can't seem to keep track of the corresponding word. I tried creating a WordFrequencyPair POJO class to store both, but then I just had a Stream<SortedSet<WordFrequencyPair>>, and I couldn't figure out how to map that into something useful.

What am I missing?