Working staff sounded timely (2,3)
I believe the answer is:
on cue
'timely' is the definition.
(I've seen this in another clue)
'working staff sounded' is the wordplay.
I cannot quite understand how this works, but
'working' could be 'on' (on can mean working or activated) and 'on' is found within the answer.
The remaining letters 'cue' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for on cue that I've seen before include "At the correct moment, like actor speaking lines" , "promptly?" , "At the appropriate moment" , "Explanation as to how something might work" , "At exactly the right moment" .)