Keep quiet about aid (8)
I believe the answer is:
preserve
'keep' is the definition.
(I know that keep can be written as preserve)
'quiet about aid' is the wordplay.
I cannot really see how this works, but
'quiet' could be 'p' (music symbol for 'piano', ie soft or quiet) and 'p' is present in the answer.
'about' could be 're' (regarding) and 're' is located in the answer.
'aid' could be 'serve' (serving is a kind of aiding) and 'serve' is found within the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for preserve that I've seen before include "Maintain - jam" , "Refuse to give up" , "Guard" , "Jam or marmalade" , "Maintain in unaltered condition" .)