Cut severely! (5)
I believe the answer is:
sever
'cut' is the definition.
(severing is a kind of cutting)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for sever that I've seen before include "Cut right off" , "Cut from a whole" , "Cut apart, maybe a relationship" , "Lop off" , "Divide, cut" .)