The fellow probing odd discharge (5)
I believe the answer is:
rheum
'discharge' is the definition.
(I know that rheum is a type of discharge)
'the fellow probing odd' is the wordplay.
'the fellow' becomes 'he' (he refers to a man).
'probing' indicates putting letters inside (probe can mean to make a hole in).
'odd' becomes 'rum' (rum can mean strange or dubious).
'he' put inside 'rum' is 'RHEUM'.
(Other definitions for rheum that I've seen before include "Discharge of water" , "Eyes watering" , "drips from the nose" , "Watery discharge from eyes or nose" , "Catarrh" .)