One hour in charge of disease (7)
I believe the answer is:
anthrax
'disease' is the definition.
(I know that anthrax is a type of animal disease)
'one hour in charge' is the wordplay.
'one' becomes 'an' (an apple is one apple).
'hour' becomes 'hr' (abbreviation).
'in' is an insertion indicator.
'charge' becomes 'tax' (tax is a kind of charge).
'hr' inserted within 'tax' is 'thrax'.
'an'+'thrax'='ANTHRAX'
'of' acts as a link.
(Other definitions for anthrax that I've seen before include "Nasty illness" , "Highly infectious, sometimes deadly, disease of cattle" , "Disease of herbivores" , "Animal disease" , "Deadly disease of sheep or cattle that can affect humans" .)