The most common and most likely answer to this crossword clue is the 16 letter word HIGH-MAINTENANCE
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Buddy explains!
The straight part
We know that "demanding a lot of attention" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case demanding a lot of attention = high-maintenance.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 HIGH-MAINTENANCE mean?
HIGH-MAINTENANCE adjective- Of a system: requiring a high degree of maintenance to ensure proper functioning, and without which it is likely to break down.
- (of a person) requiring a lot of attention or reassurance; emotionally needy