Staff happy about end of arduous projects? (6,2)

'end of arduous projects?' is the definition.
Although both the answer and definition are verbs in their -s form, I can't see how one could define the other.

'staff happy' is the wordplay.
I cannot really see how this works, but
'staff' could be 'stick' (I've seen this before) and 'stick' is present in the answer.
'happy' could be 'up' (I've seen this in other clues) and 'up' is found within the answer.
A single letter 's' remains which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).

'about' acts as a link.

Can you help me to learn more?