Article on conspiracy condenses it as this story's getting quite complicated (3,4,8)
I believe the answer is:
the plot thickens
'it as this story's getting quite complicated' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.
'article on conspiracy condenses' is the wordplay.
'article' becomes 'the' (the definite article in English).
'on' says to put letters next to each other (in a down clue, letters appear on others).
'conspiracy' becomes 'plot' (a conspiracy is a secret plot).
'condenses' becomes 'thickens' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'the'+'plot'+'thickens'='THE PLOT THICKENS'
Can you help me to learn more?
(Other definitions for the plot thickens that I've seen before include "things get less clear" , "When broader nib is used on graph paper" .)