Make a mistake and here’s a job to be done (6)
I believe the answer is:
errand
'a job to be done' is the definition.
I can't judge whether this definition defines the answer.
'make a mistake and' is the wordplay.
'make a mistake' becomes 'err' (to err is to make an error).
'err'+'and'='ERRAND'
'here's' is the link.
Can you help me to learn more?
(Other definitions for errand that I've seen before include "In purposeful trip" , "Delivery/collection trip" , "Commission, task" , "Short assignment" , "Native of a former German kingdom" .)