Medicinal plant for starters highly effective, reducing blisters (4)
I believe the answer is:
herb
'medicinal plant' is the definition.
(I've seen this before)
'starters highly effective reducing blisters' is the wordplay.
'starters' says to take the initial letters.
The first letters of 'highly effective reducing blisters' is 'HERB'.
'for' acts as a link.
(Other definitions for herb that I've seen before include "Rosemary, for example" , "Chives or coriander, say" , "Thyme, for example" , "man's name" , "Type of plant used in medicine" .)