There are two possibilities.  "job" refers to your job title, and  "job" refers to your duties.
Sam: What's your job (i.e., what's your job title)?
Pat: I'm a clerk.
Sam: What's your job (i.e., what are your duties)?
Pat: I file, type, and do other office duties.
The norm is,
Sam: What do you do?
Pat: I'm a clerk (. I work) for an insurance company.
- For Teachers