Feeling of Tiredness, Lack of Energy
Puzzle 6 of Running a Marathon Pack
Question is: Feeling of Tiredness, Lack of Energy
and the answer is: LETHARGY
Word Meaning:
LETHARGY — A state of extreme torpor, sopor or apathy, especially with lack of emotion, energy or enthusiasm; (loosely) sluggishness, laziness.
Definitions from Wiktionary.