Not possible. Addons cannot change what happens when you click on a unit in the game world.
You could compensate by running your existing macro, with minor changes,
after selecting the target:
Code:
/stopmacro [nohelp]
/focus
/targetlasttarget
/cleartarget [focus=target]
I am curious, though, how are you clicking on units in the game world so often that this is even an issue? In more than a decade of playing WoW, much of that time as a healer in raids, I can't recall
ever clicking a friendly unit in the game world on purpose...
