Burden, nuisance, a feeling of listlessness within (5)
I believe the answer is:
ennui
'listlessness within' is the definition.
I can't tell whether this definition defines the answer.
'burden nuisance a feeling' is the wordplay.
'ENNUI' is hidden within the letters.
However, I'm not sure how this is indicated.
'of' acts as a link.
(Other definitions for ennui that I've seen before include "having nothing to do" , "World-weariness" , "Mental weariness" , "Lower interest rate" , "Low interest rate" .)