Black marble lines eastern trinket (9)
I believe the answer is:
bagatelle
'trinket' is the definition.
(I have seen 'lovely trinket' mean 'bagatelle' so perhaps 'trinket' could also mean 'bagatelle')
'black marble lines eastern' is the wordplay.
'black' becomes 'b' (abbreviation as in pencil classifications).
'marble' becomes 'agate' (I've seen this in another clue).
'lines' becomes 'll' (an abbreviation for line written twice).
'eastern' becomes 'e'.
'b'+'agate'+'ll'+'e'='BAGATELLE'
(Other definitions for bagatelle that I've seen before include "Pinball game - something of little value" , "game at the tables?" , "Something trifling and negligible" , "shooting game" , "Trifling matter" .)