Smallest Planet; Chemical Once Used in Thermometers

This page is the CodyCross answer for the clue below from The 80s, Group 800, Puzzle 1 (Tears for Fears).

Question is: Smallest Planet; Chemical Once Used in Thermometers

and the answer is: MERCURY

Word Meaning:

MERCURY — (uncountable) Senses relating to the metal.

Definitions from Wiktionary.