Mission Darren messed up (6)
I believe the answer is:
errand
'mission' is the definition.
(thesaurus)
'darren messed up' is the wordplay.
'messed up' indicates an anagram.
'darren' anagrammed gives 'ERRAND'.
(Other definitions for errand that I've seen before include "Short trip with a mission" , "purposeful journey" , "run one" , "Commission, task" , "Mission usually for others" .)