Book time to tour Zambian capital (4)
I believe the answer is:
ezra
'book' is the definition.
(I've seen this before)
'time to tour zambian capital' is the wordplay.
'time' becomes 'era' (I've seen this before).
'to tour' means one lot of letters goes inside another (to tour can mean to go around).
'capital' suggests taking the first letters.
The first letter of 'zambian' is 'z'.
'era' enclosing 'z' is 'EZRA'.
(Other definitions for ezra that I've seen before include "Fifteenth book of the Old Testament" , "Jewish priest - book of the Bible" , "Old Testament book and rabbi" , "Biblical priest" , "Eponymous OT priest" .)