Covering stored in short German aircraft (6)
I believe the answer is:
glider
'aircraft' is the definition.
(glider is a kind of aircraft)
'covering stored in short german' is the wordplay.
'covering' becomes 'lid' (lid is a kind of covering).
'stored in' means one lot of letters goes inside another.
'short german' becomes 'ger' (abbreviation; 'short' suggests a short form).
'lid' put within 'ger' is 'GLIDER'.
(Other definitions for glider that I've seen before include "Engineless aircraft" , "Motorless plane" , "Kind of aircraft without an engine" , "Plane supported by air" , "Unpowered plane" .)