Cover of a glider cockpit (3)
I believe the answer is:
lid
'cover' is the definition.
(I know that lid is a type of cover)
'of a glider cockpit' is the wordplay.
'of' indicates the answer is hidden within the clue.
'LID' can be found hidden inside 'glider cockpit'.
(Other definitions for lid that I've seen before include "Removable top" , "Cover for box or eye" , "Removable cover of a container" , "Pie crust; cover" , "Kind of cover, may be hinged" .)