Bare Bones

[Babz]

Stuck on the last three then finished them all, can anyone help please with:
20A Ways of writing where Agatha's mysterious affair tok place S?E?E? (Don't really understand the clue!)
21A Greek goddess finds another one taking in female
?T?E?? (Could it be Athena?) and 18D Trees chopped up? This could measure their volume S?E??

Any help much appreciated, thanks

[orly]

20 styles
21 athene
18 stere

[kayakamina]

20a Styles........Famous novel

21a Athene......Hen in ATE (goddess)

18d Stere....anag

[Babz]

Thanks very much!! Brilliant as usual. Relax time now

[dml54]

The Mysterious Affair at Styles.

Don't you have an E where it should be a Y?

[Babz]

Yes, we did have but luckily in pencil, it was the same word but a different ending if you know what I mean, I can't remember now as it's in an envelope.