Rejecting free article must be a low point (5)
I believe the answer is:
nadir
'a low point' is the definition.
(I've seen this before)
'rejecting free article' is the wordplay.
'rejecting' shows that the letters should be reversed in order (I've seen 'reject' mean this).
'free' becomes 'rid' ('rid' can be a synonym of 'free'**).
'article' becomes 'an' (indefinite article).
'rid'+'an'='ridan'
'ridan' reversed gives 'NADIR'.
'must be' acts as a link.
(Other definitions for nadir that I've seen before include "Dinar (anag.)" , "Lowest point, or time of deepest depression." , "extremely low position" , "lowest of the low" , "Lower one cannot get!" .)