Supplement to letter about bawdy puritans (6)
I believe the answer is:
prudes
'puritans' is the definition.
('prude' can be a synonym of 'puritan')
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for prudes that I've seen before include "People with exaggerated sense of propriety" , "Persons of exaggerated propriety, too easily shocked" , "They are easily shocked by matters relating to sex" , "They're excessively concerned about propriety and decorum" , "Stuffy types" .)