Pastry, extremely sweet, ruled out (7)
I believe the answer is:
strudel
'pastry' is the definition.
(strudel is a kind of pastry)
'extremely sweet ruled out' is the wordplay.
'extremely' suggests removing the centre (only the extremes of the word are used).
'out' indicates an anagram (out can mean wrong or inaccurate).
'sweet' with its middle removed is 'st'.
'ruled' is an anagram of 'rudel'.
'st'+'rudel'='STRUDEL'
(Other definitions for strudel that I've seen before include "Dessert of thin pastry filled with fruit" , "Rolled pastry dessert" , "food" , "Fruit-filled pastry from Austria" , "German dessert" .)