Be derisive in a letter to a relative (5)
I believe the answer is:
taunt
'be derisive in' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'a letter to a relative' is the wordplay.
'a letter' becomes 't' (**).
'to a relative' becomes 'aunt' (aunt is a kind of relative).
't'+'aunt'='TAUNT'
Can you help me to learn more?
(Other definitions for taunt that I've seen before include "Bait with insulting remarks" , "Provoke; tease" , "Insult" , "Rag, goad" , "Mock, jeer" .)