The most common and most likely answer to this crossword clue is the 5 plus 3 letter word PSYCH OUT
I've seen this crossword clue in The Guardian
P
S
Y
C
H
O
U
T
More clues leading to the result PSYCH OUT
- Intimidate and turn spy with touch
- Intellectually threaten to push city’s outsiders around
- Intimidate poltroons, lacking guts and oddly touchy
- Intimidate dodgy spy with subtle touch
- Undermine film with quite even characters
- Mentally intimidate leader in pack, with youths beginning to clear off
- Play mental games on strange youth’s PC
- Leading party thrashing youths around college to intimidate
- Bully in quiet school determined to bite head of year
- Intimidate and touch spy roughly
Buddy explains!

The straight part
We know that "Intellectually threaten" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case intellectually threaten = psych out.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.