Having slap-up meal but missing first course (7)
I believe the answer is:
easting
'course' is the definition.
(I've seen this before)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for easting that I've seen before include "distance in another direction" , "distance for navigator" , "Map reference" , "oriental course?" , "distance measured" .)