Most pensions will not allow in-service withdrawals but some will allow loans. While you are working for your employer, you typically may not withdraw money from your Defined Benefit Plan.
The IRS permits plan loans if the plan administrator permits it. In-service withdrawals are possible after age 62, meaning money can get taken out before separation from service. If you leave your employer before retirement, the funds are usually kept in a Trust until you reach retirement age (or until a specified age at which you can start to receive the benefits).
In some cases, you might also lose part of these benefits. You must start to receive monthly payments the year you reach the age of 70½. However, if you start to receive payments before age 59½, you will not be subject to the 10% IRS penalty because the substantially equal payments will fall under a 72(t) exemption.