Unhappy, this writer's upset over Queen wearing fur (9)
I believe the answer is:
miserable
'unhappy' is the definition.
(similar in meaning)
'this writer's upset over queen wearing fur' is the wordplay.
'this writer's' becomes 'I'm' (the person writing the crossword clues).
'upset over' shows that the letters should be reversed in order (knocked over).
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'wearing' is an insertion indicator.
'fur' becomes 'sable' (sable is a kind of fur).
'im' back-to-front is 'mi'.
'er' going into 'sable' is 'serable'.
'mi'+'serable'='MISERABLE'
(Other definitions for miserable that I've seen before include "Depressed" , "sorrowful" , "Blue" , "Glum, wretched" , "Being sad" .)