Discharge for one set astray (5)
I believe the answer is:
egest
'discharge' is the definition.
(I know that egest is a more specific form of discharge)
'for one set astray' is the wordplay.
'for one' becomes 'eg' (both can mean 'for example').
'astray' is an anagram indicator.
'set' with letters rearranged gives 'est'.
'eg'+'est'='EGEST'
(Other definitions for egest that I've seen before include "void" , "empty" .)