Boredom shown by English nun confused this writer (5)
I believe the answer is:
ennui
'boredom' is the definition.
('ennui' can be a synonym of 'boredom')
'english nun confused this writer' is the wordplay.
'english' becomes 'e' (abbreviation).
'confused' indicates an anagram.
'this writer' becomes 'i' (the person who is writing these clues).
'nun' with letters rearranged gives 'nnu'.
'e'+'nnu'+'i'='ENNUI'
'shown by' is the link.
(Other definitions for ennui that I've seen before include "Feeling of weariness or boredom" , "Feeling when tired of life?" , "Bored listlessness" , "French boredom and lassitude" , "boring" .)