for one thing
US /fɔːr wʌn θɪŋ/
UK /fɔːr wʌn θɪŋ/

1.
para empezar, en primer lugar
used to introduce one reason, among others, for something
:
•
I can't go out tonight; for one thing, I have to study.
No puedo salir esta noche; para empezar, tengo que estudiar.
•
Why didn't you tell me? Well, for one thing, you were busy.
¿Por qué no me lo dijiste? Bueno, para empezar, estabas ocupado.