Genuine material under disturbed earth (9)
I believe the answer is:
heartfelt
'genuine' is the definition.
(thesaurus)
'material under disturbed earth' is the wordplay.
'material' becomes 'felt' (felt is a kind of material).
'under' is a charade indicator (letters next to each other) (in a down clue, some letters go below others).
'disturbed' indicates anagramming the letters (the order of letters is disturbed).
'earth' anagrammed gives 'heart'.
'felt' put after 'heart' is 'HEARTFELT'.
(Other definitions for heartfelt that I've seen before include "Most fervent in cardiac way" , "Let father have deep and earnest kind of emotion (9)" , "Kindly" , "Sincerely intended with strong feeling" , "With sincere passion" .)