The most common and most likely answer to this crossword clue is the 8 letter word DOMINION
I've seen this crossword clue in The Times
D
O
M
I
N
I
O
N
More clues leading to the result DOMINION
- Power duke has over lackey
- Subordinate after complete power
- Party functionary governed area
- Party favourite in power
- Government follower supporting party
- Circling island, something spotted, northern territory
- Party favourite comes to power
- Party underling to gain power
- Lackey following party rule
- Academic taking in dress circle’s power
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 = dominion.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 DOMINION mean?
DOMINION noun- Power or the use of power; sovereignty over something; stewardship, supremacy.
- Predominance; ascendancy
- (sometimes figurative) A kingdom, nation, or other sphere of influence; governed territory.
- An order of angel in Christian angelology, ranked above virtues and below thrones.