Half-baked dessert is hard (7)
I believe the answer is:
foolish
'half-baked' is the definition.
(I've seen this before)
'dessert is hard' is the wordplay.
'dessert' becomes 'fool' (type of dessert).
'hard' becomes 'h' (abbreviation used in pencil classifications).
'fool'+'is'+'h'='FOOLISH'
(Other definitions for foolish that I've seen before include "Unwise or ridiculous" , "Silly, lacking common sense" , "Idiotic" , "Not very bright" , "Silly, unwise" .)