The last word in conversation perhaps (7)
I believe the answer is:
goodbye
'the last' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'word in conversation perhaps' is the wordplay.
I cannot really understand how this works, but
'word' could be 'good' (good word is a kind of word) and 'good' is found within the answer.
'perhaps' could be 'y' (I've seen this in other clues) and 'y' is found in the answer.
The remaining letters 'be' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for goodbye that I've seen before include "6 Down" , "so long" , "Adieu" , "Cheerio" , "Cheers" .)