Shelter over king and national emblem (4)
I believe the answer is:
leek
'national emblem' is the definition.
(I've seen this before)
'shelter over king' is the wordplay.
'shelter' becomes 'lee' (as in lee side, the side sheltered from wind).
'over' means one lot of letters go next to another.
'king' becomes 'k' (abbreviation for king in chess).
'lee'+'k'='LEEK'
'and' is the link.
(Other definitions for leek that I've seen before include "Staffs. town; vegetable" , "Vegetable emblem of Wales" , "One of the veggies" , "Vegetable related to onions" , "Vegetable of the onion family" .)