Order a set of books for officer (10)
I believe the answer is:
commandant
'officer' is the definition.
(commandant is a kind of officer)
'order a set of books' is the wordplay.
'order' becomes 'command' (commanding is a kind of ordering**).
'a set of books' becomes 'ant'.
'command'+'ant'='COMMANDANT'
'for' acts as a link.
(Other definitions for commandant that I've seen before include "one who takes charge" , "Officer in charge of a place or group of troops" , "Military officer in charge of a place" .)