Offered position. Would be my second choice. How to hold off accepting

[Goandplay]

I interviewed for a position. They offered job last week but were out of the office until today.
I had a third interview that I should hear from today, tomorrow latest.
How can I word an email holding off giving an answer.
I don’t want to accept to have to turn down in a couple of days and mess them around. If I accepted this role I would be negotiating pay and hours so I don’t want to mess people about.

Why not thank them for the offer and ask a few questions? That might buy you a bit of time.

And email 'thank you for the offer could I just confirm XYZ please ... this will buy you a few hours

Thank you.
My first choice made an offer in time for me to email and reject their offer.

Can you not just explain that you are waiting to hear from another employer before you make a decision?

Fantastic news, congratulations :)