Unfortunately plainer chocolate filling (7)
I believe the answer is:
praline
'chocolate filling' is the definition.
(I've seen this before)
'unfortunately plainer' is the wordplay.
'unfortunately' indicates anagramming the letters.
'plainer' anagrammed gives 'PRALINE'.
(Other definitions for praline that I've seen before include "nutty dessert" , "Nutty treat" , "Smooth, nutty chocolate filling" , "Sweet stuff" , "confectionery" .)