Discharge ambassador overcome by the hard stuff (5)
I believe the answer is:
rheum
'discharge' is the definition.
(I've seen this before)
'ambassador overcome by the hard stuff' is the wordplay.
'ambassador' becomes 'HE' (His or Her Excellency).
'overcome by' means one lot of letters goes inside another.
'the hard stuff' becomes 'rum' (I can't justify this - if you can you should give a lot more credence to this answer).
'he' inserted inside 'rum' is 'RHEUM'.
Can you help me to learn more?
(Other definitions for rheum that I've seen before include "Watery discharge; sounds like space" , "Rhubarb genus; a head cold" , "Poetic tears" , "nasal discharge" , "drips from the nose" .)