Article not plausible in the least (2,3)
I believe the answer is:
at all
'in the least' is the definition.
(synonyms)
'article not plausible' is the wordplay.
I cannot really see how this works, but
'article' could be 'a' (the indefinite article in English) and 'a' is found in the answer.
The remaining letters 'tall' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for at all that I've seen before include "in any circumstances" , "in any way" , "Whatsoever" .)