It'll always be negative (5)
I believe the answer is:
never
'it'll always be negative' is the definition.
I can't tell whether this definition defines the answer.
'it'll always' is the wordplay.
'it'll' becomes 'n' (I can't explain this - if you can you should give a lot more credence to this answer).
'always' becomes 'ever' (synonyms).
'n'+'ever'='NEVER'
Can you help me to learn more?
(Other definitions for never that I've seen before include "On no occasion" , "Under no circumstances" , "'It's now or - - ' (14 song)" , "' - - Say - - Again': Bond film" , "I refuse" .)