A good universal cure ultimately for malarial fever (4)
I believe the answer is:
ague
'malarial fever' is the definition.
'a good universal cure ultimately' is the wordplay.
'a good' becomes 'ag' (I've seen this in other clues**).
'universal' becomes 'u'.
'ultimately' says to take the final letters.
The last letter of 'cure' is 'e'.
'ag'+'u'+'e'='AGUE'
'for' is the link.
(Other definitions for ague that I've seen before include "Burning fever" , "Chills and fever" , "Sweating, shivering, fit (once)" , "Sickness" , "Feverish fit" .)