Crossword puzzle clue "it may be found in a den"

It may be found in a den

One may be found in the den

They can be found in a den

Set in a den, slangily ... or, initially, what can be found in each answer to a starred clue

He opened the forty thieves' den by saying "Open sesame": 2 wds.

Den or lair

It's thrown down in a den

Lion's den?