–this only will get the name of the front application for us:
tell application “System Events” to set frontApp to name of first process whose frontmost is true

tell application “Script Editor”
–might as well go here:
activate
set a to make new document
–in case Script Editor has already one or several documents opened:
set a to the frontmost
–simple and straightforward:
set contents of document a to “tell application \”" & frontApp & “\”" & return & return & “end tell”
try
compile document a
end try
end tell
–and that’s it :), it should return true
–best of luck!

Regards,