Nonplussed after conclusion of argument, having no leeway (5-5)
I believe the answer is:
point-blank
'nonplussed after conclusion' is the definition.
The answer and definition are different parts of speech. However, adjectives and past participle verbs can occasionally define each other.
'argument having no leeway' is the wordplay.
'argument' becomes 'point' (I've seen this in another clue).
'having' is a charade indicator (letters next to each other).
'no leeway' becomes 'blank' (I can't explain this - if you can you should give a lot more credence to this answer).
'point'+'blank'='POINT-BLANK'
'of' is the link.
Can you help me to learn more?
(Another definition for point-blank that I've seen is " Abrupt, direct".)