Cruel article penned by trendy philosopher (8)
I believe the answer is:
inhumane
'cruel' is the definition.
('inhumane' can be similar in meaning to 'cruel')
'article penned by trendy philosopher' is the wordplay.
'article' becomes 'an' (indefinite article).
'penned by' means one lot of letters goes inside another.
'trendy' becomes 'in'.
'philosopher' becomes 'hume' (I've seen this in other clues**).
'in'+'hume'='inhume'
'an' placed into 'inhume' is 'INHUMANE'.
(Other definitions for inhumane that I've seen before include "Cruel" , "Not compassionate" , "Callous" , "Heartless" .)