Undercarriage (7,4)
'undercarriage' is the definition.
(landing gear is a kind of undercarriage)
This is the entire clue.
(Other definitions for landing gear that I've seen before include "Aircraft undercarriage" , "may be seen coming down to earth after flight" , "Plane's undercarriage" , "It gets you down in the end" , "Aircraft's undercarriage" .)