Roman general contracted disease (5)
I believe the answer is:
mange
'disease' is the definition.
(mange is a kind of disease)
'roman general contracted' is the wordplay.
'contracted' says the answer is hidden in the clue.
'MANGE' can be found hidden inside 'roman general'.
(Other definitions for mange that I've seen before include "Domestic animals may find it very irritating" , "Itchy disease in dogs, etc" , "Skin disease affecting hairy animals" , "disease results" , "Animal's skin disease causing loss of hair" .)