Type of onion ring found in the promised land (8)
I believe the answer is:
scallion
'type of onion' is the definition.
'ring found in the promised land' is the wordplay.
'ring' becomes 'call' ('call' can be a synonym of 'ring').
'found in' means one lot of letters goes inside another.
'the promised land' becomes 'sion' (sion or zion).
'call' placed inside 'sion' is 'SCALLION'.
(Other definitions for scallion that I've seen before include "Green onion" , "A spring onion with long neck" , "Vegetable" , "Spring 12" , "sort of onion" .)