Write untidily (6)
I believe the answer is:
scrawl
'write untidily' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for scrawl that I've seen before include "Crawls away from bad writing" , "carelessly written" , "Hasty writing" , "Long, maybe illegible, piece of writing" , "Illegible hand" .)