Boredom of nun going mad in eastern island (5)
I believe the answer is:
ennui
'boredom' is the definition.
(synonyms)
'nun going mad in eastern island' is the wordplay.
'going mad' indicates an anagram.
'in' indicates putting letters inside.
'eastern' says the letters should be written backwards (letters written right to left or east to west).
'island' becomes 'ie' (I can't justify this - if you can you should give a lot more credence to this answer).
'ie' written backwards gives 'ei'.
'nun' anagrammed gives 'nnu'.
'nnu' going into 'ei' is 'ENNUI'.
'of' is the link.
Can you help me to learn more?
(Other definitions for ennui that I've seen before include "Boredom, languor" , "The feeling of being bored" , "French boredom and lassitude" , "to make one list less when connected" , "Listless boredom" .)