Liars regularly chasing article belonging to them (5)
I believe the answer is:
their
'belonging to them' is the definition.
(I've seen this before)
'liars regularly chasing article' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'chasing' means one lot of letters go next to another (some letters chase after others).
'article' becomes 'the' (the definite article in English).
The alternating letters of 'liars' are 'ir'.
'ir' put after 'the' is 'THEIR'.
(Other definitions for their that I've seen before include "Belonging to him (perhaps wrongly)" , "Relating to them" , "belonging to an individual" , "Those people's" , "Possessive pronoun" .)