This Clock Doesn’t Work on Cloudy Days
Puzzle 15 of Famous Women in Science Hard Pack
Question is: This Clock Doesn’t Work on Cloudy Days
and the answer is: SUNDIAL
Word Meaning:
SUNDIAL — A device measuring the time of day by the position of a shadow cast by a pole or plate (gnomon) upon an engraved series of marks.
Definitions from Wiktionary.