Neither is in ignorance (3)
I believe the answer is:
nor
'neither' is the definition.
(I've seen this before)
'in ignorance' is the wordplay.
'in' says the answer is hidden in the clue.
'NOR' is hidden within 'ignorance'.
'is' is the link.
(Other definitions for nor that I've seen before include "Common conjunction, goes with neither" , "logic circuit" , "It's also not" , "Conjunction meaning 'and not'" , "Negative conjunction" .)