All I have to do is to sort out dark wool (8)
I believe the answer is:
workload
'all i have to do' is the definition.
(what a person has to work on or complete)
'sort out dark wool' is the wordplay.
'sort out' indicates anagramming the letters.
'dark'+'wool'='darkwool'
'darkwool' with letters rearranged gives 'WORKLOAD'.
'is to' acts as a link.
(Other definitions for workload that I've seen before include "Amount one has to do" , "Task(s) for a specified time" , "What's on one's plate" .)