Half-hearted meal is exceptionally good (5)
I believe the answer is:
super
'exceptionally good' is the definition.
(I've seen this before)
'half-hearted meal' is the wordplay.
'half' becomes 'supe' (I can't justify this - if you can you should believe this answer much more).
'hearted' indicates the central letters.
'meal' becomes 'curry'.
The central letter of 'curry' is 'r'.
'supe'+'r'='SUPER'
'is' acts as a link.
(Other definitions for super that I've seen before include "Prefix meaning terrific or great" , "Peachy" , "Topnotch, terrific" , "Fantastic" , "of high quality" .)