Studiously written article on a relative (6)
I believe the answer is:
thesis
'studiously written article on a relative' is the definition.
I can't tell whether this definition defines the answer.
'article on a relative' is the wordplay.
'article' becomes 'the' (the definite article).
'on' is a charade indicator (letters next to each other) (in a down clue, letters appear on others).
'a relative' becomes 'sis' (short for sister).
'the'+'sis'='THESIS'
Can you help me to learn more?
(Other definitions for thesis that I've seen before include "Learned dissertation" , "student's work" , "Theme for an essay" , "Subject" , "Treatise advancing a new point of view resulting from research" .)