Ridicule made clear in a letter (6)
I believe the answer is:
deride
'ridicule' is the definition.
(to deride is to ridicule or mock)
'made clear in a letter' is the wordplay.
'made clear' becomes 'rid' (synonyms. I am not sure about the 'made' bit.).
'in' means one lot of letters goes inside another.
'a letter' becomes 'dee' (I've seen this in another clue).
'rid' put into 'dee' is 'DERIDE'.
Can you help me to learn more?
(Other definitions for deride that I've seen before include "Test performance" , "Mock and jeer" , "Ridicule, scoff at" , "Speak of with contempt" , "'Mock, sneer at (6)'" .)