__ Deep, Deepest Part of the Tonga Trench
This page is the CodyCross answer for the clue below from Inventions, Group 45, Puzzle 2.
Question is: __ Deep, Deepest Part of the Tonga Trench
and the answer is: HORIZON
Word Meaning:
HORIZON — The visible horizontal line (in all directions) where the sky appears to meet the earth in the distance.
Definitions from Wiktionary.