Again wait on book (7)
I believe the answer is:
reserve
'book' is the definition.
(as in booking or reserving in advance)
'again wait' is the wordplay.
'again' becomes 're' (prefix meaning 'again').
'wait' becomes 'serve' (I've seen this before).
're'+'serve'='RESERVE'
'on' acts as a link.
(Other definitions for reserve that I've seen before include "Reticence" , "left on the bench?" , "Save" , "man on bench?" , "Bank" .)