The most common and most likely answer to this crossword clue is the 10 letter word APPRAISING
I've seen this crossword clue in The Sunday Telegraph
A
P
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A
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Buddy explains!

The straight part
We know that "judgmental activity" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case judgmental activity = appraising.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 APPRAISING mean?
APPRAISING verb- To determine the value or worth of something, particularly as a person appointed for this purpose.
- To consider comprehensively.
- To judge the performance of someone, especially a worker.
- To estimate; to conjecture.
- To praise; to commend.
- To apprise, inform.
- The appraisal of the value of goods, land, etc., often in order to pay the debts of a deceased person.