Voluntary? Best working for money (8)
I believe the answer is:
optional
'voluntary?' is the definition.
(I've seen this before)
'best working for money' is the wordplay.
I cannot quite see how this works, but
'best' could be 'a' and 'a' is present in the answer.
'working' could be 'on' (on can mean working or activated) and 'on' is found within the answer.
'money' could be 'p' and 'p' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for optional that I've seen before include "Platoon I join as a matter of choice" , "Not mandatory" , "Open to choice - take your pick" , "Unforced" , "'Elective, not obligatory (8)'" .)