衰
スイ, おとろ.える
decline, wane, weaken
JLPT1 G7 S10 F1432
The relevant seal inscription form is 衣 clothing + an element# indicating a straw raincoat → straw raincoat wrapped about the shoulders → *weaken*; *decline* (← straw that becomes sodden and shrinks).
[Full Kanji Etymology List]