What does lien mean in a job?
In a job, lien means a retained right to a post or a hold on something owed. Most often, an employee keeps a right to return to an earlier position while serving in another role for a period. In some contexts it also means an employer holding back dues until obligations are settled.
Lien on a post
In government and public sector service, a lien is the right of a permanent employee to hold a post even while working elsewhere on deputation or leave. The service rules of the employer define how long it lasts and what happens at the end. In private companies the word is used less often and means whatever the contract says.
Lien on dues
A few employers use lien to describe holding part of a final settlement until company property is returned or a bond is resolved. Whether and how much can be withheld depends on your contract and applicable law, so ask HR to state the clause. See the F&F settlement entry for how final dues are normally handled.
Example
A public sector employee takes a two-year deputation to another department. Her service rules let her keep a lien on her original post, so she returns to it when the deputation ends.