Medicines protecting frontlines of severely infected localities (9)
I believe the answer is:
positions
'localities' is the definition.
'medicines protecting frontlines of severely infected' is the wordplay.
'medicines' becomes 'potions'.
'protecting' is an insertion indicator.
'frontlines of' indicates taking the first letters (the letters at the front of the words).
The initial letters of 'severely infected' is 'si'.
'potions' enclosing 'si' is 'POSITIONS'.
(Other definitions for positions that I've seen before include "Places or ways of regarding things" , "Places or stands taken on issues" , "spots" .)