Feeling of chilliness initially from repellant assistant (5)
I believe the answer is:
rigor
'feeling of chilliness' is the definition.
'rigor' can be an answer for 'chilliness' (thesaurus). I am not sure about the 'feeling of' bit.
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for rigor that I've seen before include "showing failure to respond" , "Shivering chill before fever" , "Muscular cramp" , "Stiffness (after death?)" , "Chilled shivering often a symptom of disease" .)