Part-time work and extra-curriculars on Master's application CV to explain an average GPA?
Your GPA is already just one metric that may be considered in an admissions process. If you're asking whether your extracurricular activity (employment included) will be considered enough to counteract a lower-than-expected GPA, then the answer is likely No, as it's much easier to compare applicants using quantifiable values than in terms of time spent on non-academic pursuits. 

Perhaps the more important consideration is how the outside activities and work influenced your development as a student. Some of these can already go on your CV, especially if your work has any relation to your studies at all. Sometimes it's enough just to prove you can accomplish self-defined goals or learn quickly. Any accomplishments you can note on your CV can be helpful. Noting that you've been part of a sports team won't directly account for a low GPA but it hopefully improved you as a person - if it has occupied such a large part of your time that you believe you would have had a higher GPA otherwise, then perhaps it's worth mentioning elsewhere in an application, such as the cover letter.

The extra-curriculars don't matter on their own, but if they're relevant to who you are, they may be selling points on a grad school application. Your accomplishments as a student will still be the primary focus.

See also this previous question: Do non-academic extra curricular activities matter for grad school applications?