The most common and most likely answer to this crossword clue is the 5 letter word SLOTH
I've seen this crossword clue in The Times
S
L
O
T
H
More clues leading to the result SLOTH
- Opening hotel, displaying sluggishness
- Head of seminary unwilling to create sin
- Tree-dweller shot off holding end of tail.
- Languorous animal assigned position close to hearth
- Head of science reluctant to disregard absolute laziness
- Spot tail of largish New World mammal
- Son’s reluctant to become tree-climber
- Idle creature getting mum to carry large amount
- Keep quiet about a man from Sodom’s mortal sin
- Slow mover‘s eighth position?
Buddy explains!

The straight part
We know that "sluggishness" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sluggishness = sloth.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does SLOTH mean?
SLOTH noun- Laziness; slowness in the mindset; disinclination to action or labour.
- A herbivorous, arboreal South American mammal of the families Megalonychidae and Bradypodidae, noted for its slowness and inactivity.
- A collective term for a group of bears.
- To be idle; to idle (away time).