Small diamonds dropped from editorial about diamond (9)
I believe the answer is:
solitaire
'diamond' is the definition.
(solitaire is a type of diamond)
'small diamonds dropped from editorial about' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'diamonds' becomes 'd' (abbreviation for the card suit diamonds).
'dropped from' suggests deleting specific letters.
'about' indicates anagramming the letters.
'editorial' with 'd' taken out is 'eitorial'.
'eitorial' is an anagram of 'olitaire'.
's'+'olitaire'='SOLITAIRE'
(Other definitions for solitaire that I've seen before include "Card game for one player" , "Patience of Americans" , "Game for one person - single gem" , "songbird" , "game > bird" .)