The most common and most likely answer to this crossword clue is the 9 letter word OBFUSCATE
O
B
F
U
S
C
A
T
E
More clues leading to the result OBFUSCATE
- New Faces about to lose leader to Blur
- Bewilder old boy, and reportedly worry girl
- Be a fine scout, tricky to confuse
- Blur faces but nothing otherwise
- Most stubbly face disguised by oxygen mask
- Confuse most of our facts — be confused
- Blur face, but so grotesquely
- Hide cause of BT failing
- Muddle: unlikely cause of extremes of bewilderment
- Dim alumnus wore subfusc?
Buddy explains!

The straight part
We know that "Dim" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case dim = obfuscate.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 OBFUSCATE mean?
OBFUSCATE verb- To make dark; overshadow
- To deliberately make more confusing in order to conceal the truth.
- To alter code while preserving its behavior but concealing its structure and intent.
- Obfuscated; darkened; obscured.