The spice is oddly non-manic (8)
I believe the answer is:
cinnamon
'the spice is oddly non-manic' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for cinnamon that I've seen before include "Yellowish-brown - spice" , "Aromatic tree bark used as a spice" , "The spice is oddly non-manic" , "spicy stuff" , "'Spice in con man, strangely (8)'" .)