Keep piano book (8)
I believe the answer is:
preserve
'keep' is the definition.
(preserving is a kind of keeping)
'piano book' is the wordplay.
'piano' becomes 'p' (musical abbreviation).
'book' becomes 're-serve' (as in booking or reserving in advance).
'p'+'reserve'='PRESERVE'
(Other definitions for preserve that I've seen before include "Toast option" , "Keep from decay in perverse way" , "Refuse to give up" , "Maintain; keep safe" , "Protect; jam" .)