Registers one's doleful need of a job, perhaps (5,2)
I believe the answer is:
signs on
'registers' is the definition.
The answer and definition can be both to do with social activities as well as being verbs in their -s form.
Perhaps there's a link between them I don't understand?
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for signs on that I've seen before include "Employs" , "Hires" .)