Spongy, yielding (4)
I believe the answer is:
soft
I believe this is a double definition.
'spongy' is the first definition.
(similar in meaning)
'yielding' is the second definition.
(similar in meaning)
(Other definitions for soft that I've seen before include "Easily yielding to pressure" , "Mild" , "firm? On the contrary" , "Subdued - gentle" , "Tender or yielding to pressure" .)