I assumed that was what you were driving at. Of course you can read "comprise" as "consist solely of", rather than "contain or include", but I think the latter is a more commonsense interpretation (I would have preferred the word "include", actually). One could submit a solution with only the 8s without having to solve several of the clues, after all. I think the title is simply an allusion to the number in the song.
If I am wrong, and gaps are expected, I will never attempt another Listener crossword or post on here again. Are you brave enough to submit a solution with gaps?