I think 25a parses as 3-letter word for very, 4-letter word for thin, but 'evenly divided', then a four-letter word that can mean dress but not as in frock.
Delivered a hefty slap to my forehead on filling in 5a (LOI), after spending an hour lost down a rabbithole involving Bonaparte's mistresses. And then I saw the theme.
I'm puzzled by the supposed definition in 14a given that the answer as a whole has nothing to do with 'a bacon sandwich' which, as far as I know, has nothing to do with a commitment to something unseen or unknowable.
I also wondered about that. Perhaps in a whimsical way the answer might be considered as bacon (pork) in a sandwich (using the bag/pocket/pouch meaning).
Then the clue as a whole might represent two options so different that they provide an example of the answer.
Hmm…