A little tart and a cake with no filling (5)
I believe the answer is:
piece
'a little' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'tart and a cake with no filling' is the wordplay.
'tart' becomes 'pie' (both are baked goods).
'and' is a charade indicator (letters next to each other).
'with no filling' says to hollow out the word (remove centre letters).
'cake' with its middle removed is 'ce'.
'pie'+'ce'='PIECE'
Can you help me to learn more?
(Other definitions for piece that I've seen before include "wedge a > bit" , "A part of something" , "American gun" , "one of eight once ready for the Spanish?" , "Section; firearm" .)