21 down: Refuse ball-girl by chance, almost (6)
Excellent way to refer to a name: ball-girl by chance, almost = deb by risk almost = debris = refuse.
3 down: A salesman catches my aircraft, not a military ride (4, 4)
A deliciouly difficult clue that employs one of DA’s classic tricks: a salesman catches my aircraft not = a rep catches my jet no t = arep catchy myje = army jeep = a military ride.
25 across: Mighty river halved by eccentric explorer (2, 4)
Excellent sentence meaning: mighty river halved by eccentric = Amazon halved by dag = Da Gama = explorer.
6 down: Jumbo pilot wheeled meat away (6)
DA as the king of direct clues: wheeled meat away = wheeled ham out = mahout = Jumbo pilot.
12 across: Retrograde developer of modern cinema? (8, 6)
Clever cryptic definition: retrograde developer of modern cinema? = Benjamin Button.
10 across: Messiah admits sermonising, reaching out, aggravated stress (8)
Great clue that I also thought clunky at the same time: messiah admits sermonising, reaching out, aggravated = messiah admits preaching – reaching aggravated = messiah admits p aggravated = messiahp aggravated = emphasis = stress.
I think “ball girl” = DEB without any “almost”. The “almost” modifies only RISK into RIS.
That’s what I wrote, although in a compressed, idiosyncratic way that can be kind of confusing.
And I changed “risks” to “risk” (slippery S)