The most common and most likely answer to this crossword clue is the 9 letter word VEHEMENCE
V
E
H
E
M
E
N
C
E
More clues leading to the result VEHEMENCE
- Passion of macho types in Italian city, missing Northern Ireland
- Zeal is a feature of destructive he-men, certainly
- Great intensity of feeling as setter leaves Italian city, crossing European border
- Forcefulness shown by macho types overwhelming centre of European city
- Forcefulness of macho types in very English part of the Establishment
- Power held by superheroes comes after opposing evildoer first, getting forceful basically
Buddy explains!

The straight part
We know that "Power" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case power = vehemence.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 VEHEMENCE mean?
VEHEMENCE noun- An intense concentration, force or power.
- A wild or turbulent ferocity or fury.
- Eagerness, fervor, excessive strong feeling.