The First Nancy Drew Book: the __ of the Old Clock

This page is the CodyCross answer for the clue below from Space Exploration, Group 916, Puzzle 3 (Scientific Research).

Question is: The First Nancy Drew Book: the __ of the Old Clock

and the answer is: SECRET

Word Meaning:

SECRET — (countable) A piece of knowledge that is hidden and intended to be kept hidden.

Definitions from Wiktionary.

The first Nancy Drew book: The __ of the Old Clock — CodyCross Answer | CodyCross Solutions