The most common and most likely answer to this crossword clue is the 15 letter word IMPRESSIONISTIC
I've seen this crossword clue in The Times
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More clues leading to the result IMPRESSIONISTIC
Buddy explains!

The straight part
We know that "like Monet" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case like monet = impressionistic.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 IMPRESSIONISTIC mean?
IMPRESSIONISTIC adjective- Pertaining to or characterized by impressionism.
- Based on subjective reactions or feelings; not systematically researched or arrived at.
- Based on impression rather than reason or fact; based on trying to impress somebody rather than trying for accuracy.
- Impressible.