You don't need the clipboard for this. You can pass the URL straight to TextEdit. This shows you how to create and save TextEdit documents:
-- Called when script is executed
on run (argv)
-- Base name of the document without directory or file extension
-- e.g. "Important Stuff"
set documentName to "My Document"
-- Where to save new files. Default is ~/Documents
set saveDirectory to (path to documents folder)
-- Make sure this is something TextEdit understands, e.g. ".rtf", ".txt"
set fileExtension to ".rtf"
set theText to my getSafariUrl()
set thePath to my newFilePath(documentName, saveDirectory, fileExtension)
createTextEditDocument(thePath, theText)
end run
-- Create a new document containing `theText` and save it at `thePath`
on createTextEditDocument(thePath, theText)
tell application "TextEdit"
activate
make new document with properties {text:theText}
save document 1 in file thePath
end tell
end createTextEditDocument
-- Return the URL of Safari's current tab
on getSafariUrl()
tell application "Safari" to return URL of front document
end getSafariUrl
-- Return an unused filepath by appending 1,2,3 etc. to `documentName`
on newFilePath(documentName, saveDirectory, fileExtension)
set theSuffix to 1
tell application "Finder"
set fileName to (documentName as text) & fileExtension
set thePath to (saveDirectory as text) & fileName
repeat while item (thePath) exists
set fileName to (documentName as text) & " " & (theSuffix as text) & fileExtension
set thePath to (saveDirectory as text) & fileName
set theSuffix to theSuffix + 1
end repeat
end tell
return thePath
end newFilePath
