black crack
A crevice is smaller than a cave. I would go with "black crack."
Yes, a hink pink for "dark crevice" could be "gloomy groove." Both phrases feature a dark or shadowy description followed by a similar sounding word with a different meaning.
Hink-Pink is a game in which player guess a pair of rhythmic words. e.g Ocean-Lotion, Funny-Money
Dark ark is a Hink-Pink for Noah's boat with the lights off.
black sack
dark park
night sight
tan man, Dark Mark
gray day, bleak weekgray day, bleak week
Fake bake is a Hink-Pink for counterfeit cook.
Thin inn is the hink pink for skinny hotel.
The Hink Pink for a holiday donkey is a Yule mule.