Romeo appears in silly sketch (5)
I believe the answer is:
draft
'sketch' is the definition.
(I know that draft is a type of sketch)
'romeo appears in silly' is the wordplay.
'romeo' becomes 'R' (phonetic alphabet: alpha, bravo, charlie etc.).
'appears in' indicates putting letters inside.
'silly' becomes 'daft' (I've seen this in another clue).
'r' inserted within 'daft' is 'DRAFT'.
(Other definitions for draft that I've seen before include "Draw an outline" , "Preliminary drawing" , "Preliminary outline" , "Send" , "Preliminary version or sketch" .)