Comedian digesting beginning of royal court document (4)
I believe the answer is:
writ
'court document' is the definition.
(I've seen this in another clue)
'comedian digesting beginning of royal' is the wordplay.
'comedian' becomes 'wit' (a witty person).
'digesting' is an insertion indicator (inserted letters are eaten or ingested).
'beginning of' indicates taking the first letters.
The initial letter of 'royal' is 'r'.
'wit' going around 'r' is 'WRIT'.
(Other definitions for writ that I've seen before include "What scribe did" , "Legal document, usually served" , "Legal document of command" , "Legal order in writing" , "Veteran composed" .)