A permanent negative (5)
I believe the answer is:
never
If this is the answer, I'm afraid I cannot explain it.
Can you help me to learn more?
(Other definitions for never that I've seen before include "Under no circumstances" , "' - - Say - - Again': Bond film" , "Not in a month of Sundays" , "At no time in the past or future" , "Emphatic negative" .)