Document mostly deconstructed minor style of drama (4,4)
I believe the answer is:
film noir
'style of drama' is the definition.
(film genre)
'document mostly deconstructed minor' is the wordplay.
'document' becomes 'file' (a file is a formal document).
'mostly' means to remove the last letter.
'deconstructed' indicates anagramming the letters (letters put back together in a new way).
'file' with its last letter removed is 'fil'.
'minor' anagrammed gives 'mnoir'.
'fil'+'mnoir'='FILM NOIR'
(Other definitions for film noir that I've seen before include "1940s' genre of American thriller or detective movies (French)" , "American thriller or detective movie style of the '40s and '50s" , "Dark cinema genre" , "Bleak style of movie" .)