Forefinger (5)
I believe the answer is:
index
'forefinger' is the definition.
(I know that forefinger can be written as index)
This is all the clue.
(Other definitions for index that I've seen before include "Alphabetical listing in a book" , "List of subjects in book" , "Alphabetical guide" , "Alphabetical list of a book's contents" , "Alphabetica listing" .)