Easily swayed (4-6)
'easily swayed?' is the definition.
The answer and definition are different parts of speech. However, past participle verbs and adjectives occasionally mean the same thing.
This is the entire clue.
Can you help me to learn more?
(Other definitions for supple that I've seen before include "Mobile" , "Lithe and flexible" , "Opposite of stiff" , "Pliant, flexible" , "Flexible, not stiff" .)