smart default value for custom field or work around

Question

I have additional custom field assigned to issue "Customer"
I have additional custom field in project "Customer"

I need a rule that if I define "Customer" in Project - in the issue view I will have selected default Customer as I choose in Project.

I have cloud version. 
Maybe someone can lead me to the dissolution?

a) It should be a script which will be trigger by some listener 
b) I should read about smart value
c) I should use some plugin? 
or other solution.

Thanks for help!

Magdalena Zhisheva · Answer

Hi @Tomasz Fąfara ,

Can you give some more details on this question:

What is the default value, which is required?

I really can't get this " I need a rule that if I define "Customer" in Project - in the issue view I will have selected default Customer as I choose in Project."

Can you give some example?