An action that covers just about anything to do with sorting out yourself, your kit or those around you. For example, 'I'm off to do some admin' can mean:
2. I'm off to unpack/ repack/ adjust/ readjust my kit or bedspace.
3. I'm off to clean something.
4. I'm going for a kip.
In rare cases, it could apply to doing paperwork, but use of the term is to be discouraged. In these circumstances, the term 'work' may be substituted.