Suffering from interminable preoccupation is hard (7)
I believe the answer is:
anguish
'suffering' is the definition.
(I know that anguish is a type of suffering)
'interminable preoccupation is hard' is the wordplay.
'interminable' says to take the centre (the ends or 'terminuses' of the word are removed).
'preoccupation' becomes 'hang-up' (a hang-up is a preoccupation or neurosis).
'hard' becomes 'h' (abbreviation used in pencil classifications).
The middle letters of 'hangup' are 'angu'.
'angu'+'is'+'h'='ANGUISH'
'from' is the link.
(Other definitions for anguish that I've seen before include "Severe mental distress" , "Heartache, great distress" , "Mental torment" , "Great (mental) pain" , "Extreme misery" .)