Textbook section
'textbook section' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for unit that I've seen before include "Single person - group of people" , "Single item; one" , "Self-contained part" , "Individual thing; one" , "Module" .)
'textbook section' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for index that I've seen before include "Forefinger" , "Alphabetical register" , "List of topics etc" , "that may be on the cards?" , "Type of glossary" .)