On a mission, with vacuous engineer, to get paid in Cape Town (6)
I believe the answer is:
errand
'paid in cape town' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'on a mission with vacuous engineer' is the wordplay.
'on' means one lot of letters go next to another.
'a mission with' becomes 'rand' (I can't explain this - if you can you should give a lot more credence to this answer).
'vacuous' suggests removing the centre.
'engineer' with its centre taken out is 'er'.
'rand' after 'er' is 'ERRAND'.
'to get' is the link.
Can you help me to learn more?
(Other definitions for errand that I've seen before include "Messenger's job" , "Short trip for a message" , "Short assignment" , "Journey made on someone else's behalf" , "Commission, task" .)