Yes, Acacia dunnii. It can be invasive. But it's a native to an area about 400 to 500 kms from here so people plant it as a native. Strictly that's not correct but people like it. I suspect mine came in with earthmoving equipment when I had some excavations done. There's no others around the neighbourhood that I've noticed. After flowering I cut off any seed pods forming but it's getting too tall now. Looks like a chainsaw job coming up soon.

acacias are sneaky, their roots get everywhere and start new plants.

A homeowner near where I used to live kept complaining about flowers and leaves from an acacia on county-owned land near his house. The county did nothing about it, so the homeowner girdled the tree to kill it. The roots sent up hundreds of new trees, damaging the house foundation. Typically, the homeowner sued the county.

Perhaps you should plan on using a systemic poison when you cut the tree.

That wouldn't have been an Acacia, they don't sprout from roots. They have a fairly weak root system. Although, possibly they were seedlings, not from the root system. When tree canopy is removed a lot of dormant seeds will spring to life.

Acacias are a legume and add a lot of nitrogen into the soil. Growing well on very poor and disturbed soils they're good as pioneer plants in rehabilitation.

interesting. I wonder what it was.

There's a number of plants with flowers like Acacia. But I don't know of any with the characteristics you've mentioned.