Just as you'd think, this oration is from the mouth (6)
I believe the answer is:
expect
'just as you'd think this oration' is the definition.
The definition and answer are not the same part of speech.
'from the mouth' is the wordplay.
'from' becomes 'ex' ('from' in Latin).
'the mouth' becomes 'pect' (I can't justify this - if you can you should give a lot more credence to this answer).
'ex'+'pect'='EXPECT'
'is' is the link.
Can you help me to learn more?
(Other definitions for expect that I've seen before include "Suppose, assume" , "Hope - await" , "Envision or await" , "Be pregnant" , "demand and > have prospects" .)