The most common and most likely answer to this crossword clue is the 8 letter word PARANOIA
I've seen this crossword clue in The Guardian
P
A
R
A
N
O
I
A
More clues leading to the result PARANOIA
- Answer Scottish island charge after mounting, baseless fear
- Soldier on holiday regularly experienced irrational fear
- Suspicion a denial penned by outcast’s inconclusive
- Intense fear as norm I found in wild ox
- Dad managed alternatively logical and unjustified suspicion
- Quietly a prince admits love, one sort of obsession
- Soldier number one has a psychological condition
- A Scottish island hit back, showing irrational fear
- Soldier guarding Scottish Island reflected sense of foreboding
- Delusions of roughly spoken person who bothers couples
Buddy explains!

The straight part
We know that "unjustified suspicion" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case unjustified suspicion = paranoia.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 PARANOIA mean?
PARANOIA noun- A psychotic disorder characterized by delusions of persecution, conspiracy and perceived threat against the person, often associated with false accusations and general mistrust of others
- Extreme, irrational distrust of others.