Spice teachers initially misidentified, say (6)
I believe the answer is:
nutmeg
'spice' is the definition.
(nutmeg is a kind of spice)
'teachers initially misidentified say' is the wordplay.
'teachers' becomes 'nut' (National Union of Teachers).
'initially' indicates taking the first letters.
'say' becomes 'eg'.
The initial letter of 'misidentified' is 'm'.
'nut'+'m'+'eg'='NUTMEG'
(Other definitions for nutmeg that I've seen before include "Hard seed of tropical tree ground as spice" , "it's used by bakers" , "Hard seed used as seasoning" , "Aromatic seed - met gnu (anag)" , "Spicy seasoning - hard fruit for little Margaret?" .)