The most common and most likely answer to this crossword clue is the 13 letter word UNDERESTIMATE
I've seen this crossword clue in Independent
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More clues leading to the result UNDERESTIMATE
- Erudite men sat around — judge not well?
- Surprisingly, erudite man set value too low
- Inadequate assessment of semi-nude art arranged on Tate’s walls
- Erudite men sat around giving inferior judgement
- Dismiss United with resident team playing
- Disparage mates in duet badly covering Queen
- Assign a low value to muted trainees in disarray
- Fail to appreciate foreign articles one’s imported by car
Buddy explains!

The straight part
We know that "Inadequate assessment" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case inadequate assessment = underestimate.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 UNDERESTIMATE mean?
UNDERESTIMATE noun- An estimate that is too low.
- To perceive (someone or something) as having a lower value, quantity, worth, etc., than what he/she/it actually has.