One leading royal appearing in silly sketch (5)
I believe the answer is:
draft
'sketch' is the definition.
(draft is a kind of sketch)
'one leading royal appearing in silly' is the wordplay.
'one leading' indicates taking the first letters.
'appearing in' means one lot of letters goes inside another.
'silly' becomes 'daft' (I've seen this in another clue).
The initial letter of 'royal' is 'r'.
'r' going inside 'daft' is 'DRAFT'.
(Other definitions for draft that I've seen before include "conscript" , "Preliminary drawing" , "Provisional document" , "Preliminary outline" , "Early version of text" .)