Short trip to perform a task (6)
I believe the answer is:
errand
'short trip to perform a task' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for errand that I've seen before include "Job usually involving a short trip" , "A little job" , "Short journey on behalf of another" , "Mission usually for others" , "Mission (usually run!)" .)