Rook in appropriate flying machine (5)
I believe the answer is:
drone
'flying machine' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe you can see a link between them that I can't see?
'rook in appropriate' is the wordplay.
'rook' becomes 'R' (chess abbreviation).
'in' indicates putting letters inside.
'appropriate' becomes 'done' (I can't explain this - if you can you should give a lot more credence to this answer).
'r' placed inside 'done' is 'DRONE'.
Can you help me to learn more?
(Other definitions for drone that I've seen before include "Sustained bass note accompanying a melody - male bee" , "Idler or male honey-bee" , "Monotonous sound - member of hive" , "Continuous sound; bee" , "RPV" .)