Special terms must include change (5)
I believe the answer is:
alter
'change' is the definition.
('alter' can be a synonym of 'change')
'special terms must include' is the wordplay.
'include' indicates the answer is hidden within the clue.
'ALTER' is hidden within 'special terms must'.
(Other definitions for alter that I've seen before include "Alert to change" , "Change or adjust" , "shift" , "Change, maybe later" , "Metamorphose" .)