Ceremony set down on paper as it is said (4)
I believe the answer is:
rite
'ceremony' is the definition.
(I know that rite is a type of ceremony)
'set down on paper as it is said' is the wordplay.
I cannot really understand how this works, but
'paper' could be 'i' (UK newspaper) and 'i' is present in the answer.
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is found within the answer.
'on' could be 're' ('on' can be mean 'with reference to') and 're' is located in the leftover letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for rite that I've seen before include "Formal procedure" , "(Words for) ceremony" , "Solemn ceremony" , "(Words used in) ceremonial" , "Religious ceremonial sounds correct" .)