A mushroom's is called a pileus (3)
I believe the answer is:
cap
(Other definitions for cap that I've seen before include "Beat; upper limit" , "Soft headgear" , "Impose limit on" , "Top; hat" , "Better; hat" .)
I believe the answer is:
cap
(Other definitions for cap that I've seen before include "Beat; upper limit" , "Soft headgear" , "Impose limit on" , "Top; hat" , "Better; hat" .)