Though hesitant to take undue rests, they aren't good at their work (8)
I believe the answer is:
shysters
'though hesitant to take undue' is the definition.
I can't tell whether this definition defines the answer.
'rests they aren't good at their work' is the wordplay.
I cannot really see how this works, but
an anagram of 'rests' is 'sters' which is present in the answer.
The remaining letters 'shy' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for shysters that I've seen before include "Persons (politicians or lawyers?) who cut corners" , "Lawyers or politicians who use unethical methods" , "People who act unprofessionally or unscrupulously" , "Unscrupulous people" .)