The most common and most likely answer to this crossword clue is the 8 letter word OVERBEAR
I've seen this crossword clue in The Sunday Telegraph
O
V
E
R
B
E
A
R
Buddy explains!

The straight part
We know that "Be domineering" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case be domineering = overbear.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 OVERBEAR mean?
OVERBEAR verb- To carry over.
- To push through by physical weight or strength; to overwhelm, overcome.
- To prevail over; to dominate, overpower; to oppress.
- To produce an overabundance of fruit.