Left personal documents in German aircraft (6)
I believe the answer is:
glider
'aircraft' is the definition.
(glider is a kind of aircraft)
'left personal documents in german' is the wordplay.
'left personal documents' becomes 'lid' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'in' means one lot of letters goes inside another.
'german' becomes 'ger' (abbreviation).
'lid' put within 'ger' is 'GLIDER'.
Can you help me to learn more?
(Other definitions for glider that I've seen before include "Unpowered aircraft" , "Powerless traveller" , "Powerless aircraft" , "quiet flier" , "Kind of aircraft without an engine" .)