Nous about task (4)
I believe the answer is:
onus
'task' is the definition.
(I've seen this in another clue)
'nous about' is the wordplay.
'about' is an anagram indicator.
'nous' is an anagram of 'ONUS'.
(Other definitions for onus that I've seen before include "'Burden, load (4)'" , "Responsibilty" , "Capulet opponent (R&J)" , "Encumbrance" , "Liability" .)