Tiredness seen in pupil regularly (5)
I believe the answer is:
ennui
'tiredness' is the definition.
(I've seen this before)
'seen in pupil regularly' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'seen'+'in'+'pupil'='seeninpupil'
The alternate letters of 'seeninpupil' are 'ENNUI'.
(Other definitions for ennui that I've seen before include "tiredness" , "Bored listlessness" , "Effect of boredom" , "Listless feeling" , "Low interest rate" .)