Refuse the first outbreak (5)
I believe the answer is:
trash
'refuse' is the definition.
(both can mean rubbish)
'the first outbreak' is the wordplay.
'the first' becomes 't' (1st letter of 'the').
'outbreak' becomes 'rash' (rash can mean a sudden outbreak).
't'+'rash'='TRASH'
(Other definitions for trash that I've seen before include "Rubbish, waste" , "Worthless material to be disposed of" , "Worthless items" , "Refuse; wreck" , "Anything of poor quality" .)