Weakness

ANEMIA

This medical condition often results from iron deficiency and can leave you feeling unusually tired or short of breath.

Anemia" fits "weakness" because it’s a medical condition where the blood lacks enough healthy red blood cells, leading to fatigue and low energy. The clue plays on the literal meaning of weakness—both physical tiredness and the broader sense of vulnerability—while the answer is a precise term doctors use for that exact issue. No wordplay here, just a direct connection between a common symptom and its clinical name.