It can go on spreading disease (9)
I believe the answer is:
contagion
'disease' is the definition.
(contagion is a kind of disease)
'it can go on spreading' is the wordplay.
'spreading' is an anagram indicator.
'it'+'can'+'go'+'on'='itcangoon'
'itcangoon' with letters rearranged gives 'CONTAGION'.
(Other definitions for contagion that I've seen before include "cause of widespread ill-feeling" , "Communication of disease by close contact" , "Infection" , "Cognation (anag.)" .)