Representative time with a book (5)
I believe the answer is:
agent
'representative' is the definition.
(agent is a kind of representative)
'time with a book' is the wordplay.
'time' becomes 't' (abbreviation).
'with' is a charade indicator (letters next to each other).
'book' becomes 'gen' (I've seen this in other clues).
'a'+'gen'='agen'
't' put after 'agen' is 'AGENT'.
(Other definitions for agent that I've seen before include "One acting on behalf of another" , "One does business on behalf of another" , "Operative" , "Business manager" , "factor in Scotland" .)