Guardian 28021

[Pete666]

I think we've finished it but can't quite parse one clue:
13a If letters were missing, this could be the fourth character of eight in a string (10)
We think it's apostrophe. We can see the 4th character in eight (H) in a rope. Leaves 'post' to clue..

[Lie-in King]

If letters were missing, you'd get - A'rophe

[Pete666]

OK Lie-in, thanks. Actually the 'letters missing' could be the post, yeah?

[Lie-in King]

Yes, post; letters; mail - I didn't do the rest as you already had it :-)

[Jackdaw33]

Post can mean letters, mail. Take out the post and you have a rophe.

[Pete666]

Yes, got it! I actually quite enjoyed this puzzle, thanks Puck; was a bit of fun