We usually eschew end-of-clue punctuation, even when we manage to have a clue that is a bona fide sentence, as in this example:
   EMIGRANTS  They have moved away from streaming illegally (9)

One exception is the exclamation point; as is standard in American cryptic usage, we generally use that to indicate an &lit clue. But the more common exception is the question mark. At the end of a clue, it can indicate quite a few different things. Sometimes it signals a jokey or punny definition (either the main one or the second part of a double-definition clue):
   ANDROCLES  Mythical bird, originally living in a mountain range with amateur

   veterinarian? (9)

   DEMOCRATIC PARTY  A pretty rad comic playing the blues? (10,5)
   GREAT DEPRESSION  Economic catastrophe in the Grand Canyon? (5,10)
   HARD TIMES  1854 novel in the print edition of a newspaper? (4,5)

Sometimes it indicates a heteronymic reading of the entry:
   ANTIQUITY  In olden times, a health club that won’t let you give up? (9)
   HATRACK  Something you might see in the front hall or hear on a sitcom? (7)

It might flag a reading that is far-fetched or unexpected:
   ASSESSES  Rates female donkeys? (8)
   COOPERATION  Teamwork in making barrels? (11)
   DEMEANING  Shameful process of making people nicer? (9)

…or even absurd or ridiculous:
   ACTIVIST  Militant whose favorite part of a Shakespeare play is the penultimate section? (8)
   BUCOLIC  Rural ailment afflicting infants at a New England school? (7)
   CORONATION  Installation of a sovereign in Chad or Oman? (10)
   FOREARMED  Prepared, like, half an octopus in the sound? (9)
   HAMBURGER  One who encourages second choice for pork as a fast-food standard? (9)

A question mark could reveal that we suspect someone out there will object to a clue they will deem, well, questionable:
   FREE THROW  Worth undertaking after a foul? (4,5)
   DETERGENT  Barman’s cleanser? (9)
   GOLDENEYE  Objective: refuse to be heard in a thriller about a duck? (9)

In short, all you can conclude from a question mark is that “something is going on here.” Or not! Sometimes a question mark is just a question mark:
   CROSSWORD  Sorcerer, half looking back at weapon: “You’re wasting your time with

   this?” (9)

This week’s cluing challenge: INTERROGATE. To comment (and see other readers’ comments), please click on this post’s title and scroll to the bottom of the resulting screen. And now, four links:
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• Our puzzle-solving guidelines | PDF
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