Guaranteed essentially filling food from part of Scandinavia (6)
I believe the answer is:
danish
'from part of scandinavia' is the definition.
'guaranteed essentially filling food' is the wordplay.
'essentially' indicates the central letters.
'filling' means one lot of letters goes inside another.
'food' becomes 'dish' (dish is a kind of food).
The middle letters of 'guaranteed' are 'an'.
'an' going inside 'dish' is 'DANISH'.
(Other definitions for danish that I've seen before include "European language" , "Relating to Denmark" , "course includes article / noun combination" , "Hamlet was and bacon may be" , "Had sin with this nationality?" .)