Harass in open palaver, left with fever and shivering fit (6)
I believe the answer is:
plague
'harass in open palaver' is the definition.
'plague' can be an answer for 'harass' (synonyms). I am not certain of the 'in open palaver' bit.
'left with fever and shivering fit' is the wordplay.
'left' becomes 'l' (common abbreviation).
'with' says to put letters next to each other.
'fever' becomes 'p' (I can't explain this - if you can you should give a lot more credence to this answer).
'and' is a charade indicator (letters next to each other).
'shivering fit' becomes 'ague' (I've seen this in another clue).
'l' put after 'p' is 'pl'.
'pl'+'ague'='PLAGUE'
Can you help me to learn more?
(Other definitions for plague that I've seen before include "dog" , "Epidemic (the "Great" one being in 1665)" , "Afflict" , "Annoy continually" , "Contagious disease that spreads rapidly and kills many" .)