The shivers, the endless runs and ailments (7)
I believe the answer is:
thrills
'the shivers' is the definition.
('thrill' can be a synonym of 'shiver')
'the endless runs and ailments' is the wordplay.
'endless' means to remove the last letter.
'runs' becomes 'r' (cricket abbreviation).
'and' means one lot of letters go next to another.
'ailments' becomes 'ills' ('ill' can be a synonym of 'ailment').
'the' with its last letter removed is 'th'.
'th'+'r'+'ills'='THRILLS'
(Other definitions for thrills that I've seen before include "Waves of excited feelings" , "Excites" , "Exciting sensations" , "Delights" , "Hair-raising experiences" .)