Rich cake a part of breakfast or tea (5)
I believe the answer is:
torte
'rich cake' is the definition.
(I've seen this before)
'a part of breakfast or tea' is the wordplay.
'a part of' indicates the answer is hidden within the clue.
'TORTE' is hidden in the letters of 'breakfast or tea'.
(Other definitions for torte that I've seen before include "Sweet cake or tart" , "Rich sweet cake" , "Rich food" , "(Austrian) cake with cream and fruit or nuts" , "Rich (Austrian) cake or pastry" .)