The most common and most likely answer to this crossword clue is the 9 letter word LETHARGIC
I've seen this crossword clue in Independent
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More clues leading to the result LETHARGIC
- In play, Charlie gets oddly sluggish
- Teach girl to embroider, but she’s idle
- Sluggish husband getting into scrape left upset and sick at heart
- The garlic could make one sluggish
- Listless learner, I gather, suffering with cold
- Drowsy, left the cigar to go out
- Teach girl cooking, with little response
- Sluggish mobile – charge it after end of call
- Mostly thick, large, clumsy and sluggish
- Listless girl cheat upset
Buddy explains!

The straight part
We know that "sluggish" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sluggish = lethargic.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 LETHARGIC mean?
LETHARGIC adjective- Sluggish, slow
- Indifferent, apathetic