Boredom seen in pupil regularly (5)
I believe the answer is:
ennui
'boredom' is the definition.
(I know that boredom can be written as ennui)
'seen in pupil regularly' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'seen'+'in'+'pupil'='seeninpupil'
The alternating letters of 'seeninpupil' are 'ENNUI'.
(Other definitions for ennui that I've seen before include "French boredom and lassitude" , "Listless boredom" , "Weary feeling" , "Feeling of dissatisfaction" , "Feeling of disaffection" .)