Figure pathogen's spread (8)
I believe the answer is:
heptagon
'figure' is the definition.
(heptagon is a kind of figure)
'pathogen's spread' is the wordplay.
'spread' is an anagram indicator.
'pathogen' with letters rearranged gives 'HEPTAGON'.
(Other definitions for heptagon that I've seen before include "Seven-sided object" , "Seven-sided shape" , "Seven-sided figure" , "A geometric figure with seven sides" .)