The would-be expert punned the thing spoken of (6)
I believe the answer is:
pundit
'the would-be expert' is the definition.
'pundit' can be an answer for 'expert' (I've seen this in another clue). I am not sure about the 'the would-be' bit.
'punned the thing spoken of' is the wordplay.
I cannot quite understand how this works, but
'thing' could be 'it' and 'it' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for pundit that I've seen before include "Learned Hindu or general expert" , "A learned Hindu or expert generally" , "A learned person of Hindu origin?" , "Pontificating expert" , "Talking expert" .)