Serious cut on end of nose (6)
I believe the answer is:
severe
'serious' is the definition.
(I know that serious can be written as severe)
'cut on end of nose' is the wordplay.
'cut' becomes 'sever' (to sever is to cut or split).
'on end of nose' becomes 'e' (I can't explain this - if you can you should believe this answer much more).
'sever'+'e'='SEVERE'
Can you help me to learn more?
(Other definitions for severe that I've seen before include "sober" , "Taxing" , "Harsh and unbending" , "Harsh and exacting" , "Extreme - strict" .)