A Questioning Clue?

[Glenn9999]

While trying to be cute, the subject above catches the entirety of my question:

Are there any kind of rules involved on what clues earn a "?" after them? (this occurred to me, and after looking at several puzzles, I really can't see an ironclad rule in operation...)

[4wd]

"?" means the clue's not to be taken literally, word play or some other form of funny
business is taking place, if you've got a really tricky/funny clue that's dances around
 an entry's definition its "?" worthy

[Glenn9999]

Okay.  Usually my confusion (and why I ask) is that I encounter many clues that using that definition (or other common ones which deserve the "?" if "funny business" is the measure.  Guess it depends on how you define "funny business"?

[4wd]

Yup, it's a pretty subjective matter, if you think a particular clue needs one, then by all means add it, though what I tend to do is to check out the clue database. Sometimes a previous constructor would've clued the entry in a similar way and if a ?'s in play then you're on the
right path.