General weariness is some rotten nuisance (5)
I believe the answer is:
ennui
'general weariness' is the definition.
'ennui' can be an answer for 'weariness' (ennui is weariness or boredom). I am not sure about the 'general' bit.
'some rotten nuisance' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'ENNUI' is hidden in the letters of 'rotten nuisance'.
'is' is the link.
Can you help me to learn more?
(Other definitions for ennui that I've seen before include "Listless feeling" , "Boredom in France" , "Weariness with life" , "French boredom and lassitude" , "Effect of boredom" .)