Request comes in to get engine part (6)
I believe the answer is:
Here is my best explanation:
'engine part' is the definition.
'request comes in to get' is the subsidiary indication.
'request' becomes 'ask' ('ask' can be a synonym of 'request').
'comes in to' means one lot of letters goes inside another.
'get' becomes 'get' (**).
'ask' going into 'get' is 'gasket'.
(Other definitions for gasket that I've seen before include "external sealing device", "Flat metal seal between tow surfaces as of engine", "Engine seal", "Packing piece used as seal in metal joint", "(Engine) sealing sheet", "Ring for sealing a pipe joint", "Seal for a pipe joint", "Sealing ring", "Compressible piece of rubber forming a seal" and "Tow used for packing a piston".)