Sorry on it's own this answer I've given doesn't make sense.
The clue is 19a) and reads: 13 - selfishly? (6).
The answer to 13a) may have a bearing n the solution.
The clue for 13a) is: Avoid nearly all cheese grated by wife (6).
(I have an answer for this as well which I think begs the question in 19a)