The short answer
Send a close-up and wider photo, identify the driveway material if known, and tell the provider how long the stain has been there. Ask for a realistic expected improvement and whether a test is needed.
Identify the driveway first
Block paving, concrete, resin-bound surfacing and tarmac need different assessments. Give the product or installer details if available. Include any sealant, coating or previous cleaning treatment you know about. An unknown surface should be assessed rather than treated as a default material.
Explain what happened
Say whether the leak is continuing, when the mark appeared and what has already been applied. A photograph cannot reliably establish the substance or how deeply it has affected the surface. Avoid adding another household treatment while waiting for advice, especially if the first product is unknown.
Ask what the quote promises
There is a meaningful difference between cleaning the surrounding dirt, reducing a stain and removing every visible trace. Ask the provider to describe the target result and any limits before you book. If a test area is proposed, agree how its outcome will affect the rest of the work and the price.
Consider the whole driveway
Cleaning only a patch can leave an obvious difference from surrounding paving. Ask how a local treatment and wider clean would compare, without assuming either will produce a uniform new finish. Include drains, vehicles and neighbouring surfaces in the work brief.
Agree the aftercare
Ask when vehicles can return and whether any jointing or finishing work is needed for your surface. Keep these instructions with the selected quote. If a leak is still occurring, address that separately so the cleaned area is not immediately stained again.