Greek characters contributing to the task (4)
I believe the answer is:
etas
'greek characters' is the definition.
(eta is a Greek letter)
'contributing to the task' is the wordplay.
'contributing to' says the answer is hidden in the clue (the answer contributes to part of the clue ).
'ETAS' can be found hidden inside 'the task'.
(Other definitions for etas that I've seen before include "Foreign characters" , "Makarios' letters" , "Characters in Greece" , "lowly workers" , "who once did menial tasks in Japan?" .)