Can be said to be the opposite of taint (3)
I believe the answer is:
tis
'can be said to' is the definition.
I can't tell whether this definition defines the answer.
'the opposite of taint' is the wordplay.
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
'opposite of taint' becomes 'is' (I can't justify this - if you can you should believe this answer much more).
't'+'is'='TIS'
'be' is the link.
Can you help me to learn more?
(Other definitions for tis that I've seen before include "Contraction of it is" , "I confirm the identity of" , "Sequel to "Angela's Ashes"" , "That thing's" , "McCourt work" .)