Amusement park? First book on it turned up (6)
I believe the answer is:
tivoli
'amusement park?' is the definition.
(Tivoli Gardens, amusement park in Copenhagen)
'first book on it turned up' is the wordplay.
'first book' becomes 'vol I' (first volume).
'on' says to put letters next to each other.
'turned up' shows that the letters should be reversed in order.
'it' back-to-front is 'ti'.
'voli' after 'ti' is 'TIVOLI'.
(Other definitions for tivoli that I've seen before include "Site of the Villa d'Este" , "Town near Rome; gardens in Copenhagen" , "Pleasure garden in Copenhagen" , "old Italian town" , "Copenhagen park" .)