Cake that is cooked with no topping (5)
I believe the answer is:
scone
'cake' is the definition.
(scone is a type of cake)
'that is cooked with no topping' is the wordplay.
'that is' becomes 'sc' (abbrv. for Latin scilicet; 'namely').
'cooked' becomes 'done' (similar in meaning).
'with no topping' means to remove the first letter.
'done' with its first letter removed is 'one'.
'sc'+'one'='SCONE'
(Other definitions for scone that I've seen before include "Scottish location" , "Product of baker" , "Plain teatime cake" , "Tea-time treat" , "Plain cake (for Scottish kings?)" .)