That's fine - there's nothing left (8)
I believe the answer is:
allright
'that's fine there's nothing left' is the definition.
I know nothing about this answer so I can't tell whether this works.
'that's fine there's nothing left' is the wordplay.
'that' becomes 'all' (I can't justify this - if you can you should give a lot more credence to this answer).
'fine' becomes 'righto' (both can mean 'yes' or 'alright').
'there's nothing' becomes 'o' (I've seen this in other clues).
'left' indicates named letters should be taken away (some letters have left).
'righto' with 'o' removed is 'right'.
'all'+'right'='ALLRIGHT'
Can you help me to learn more?
(Other definitions for allright that I've seen before include "Very well" , "None left" .)