Points out an article that's weak (3)
I believe the answer is:
wan
'weak' is the definition.
('wan' can be similar in meaning to 'weak')
'points out an article' is the wordplay.
'points' becomes 'wn' (**).
'out' is an insertion indicator.
'an article' becomes 'a' (indefinite article).
'wn' going around 'a' is 'WAN'.
'that's' is the link.
(Other definitions for wan that I've seen before include "Pale and pinched-looking" , "Faint" , "Pale and looking ill" , "Pale and ill-looking" , "Pasty" .)