A sweet smile on a new development (8)
I believe the answer is:
semolina
'a sweet' is the definition.
(I've seen this before)
'smile on a new development' is the wordplay.
'a new' is an anagram indicator.
'development' becomes 'a' (I can't explain this - if you can you should give a lot more credence to this answer).
'smile'+'on'='smileon'
'smileon' anagrammed gives 'semolin'.
'semolin'+'a'='SEMOLINA'
Can you help me to learn more?
(Other definitions for semolina that I've seen before include "Hard particles of wheat used in puddings etc" , "A lemon is used in the pudding, strangely" , "Pudding flour" , "Form of wheat for puddings" , "sweet" .)