Hum about eastern king (4)
I believe the answer is:
reek
'hum' is the definition.
(thesaurus)
'about eastern king' is the wordplay.
'about' becomes 're' ('re' means regarding or about).
'eastern' becomes 'e'.
'king' becomes 'K' (chess abbreviation).
're'+'e'+'k'='REEK'
(Other definitions for reek that I've seen before include "bad odour" , "smoke in Balmoral" , "Smell bad" , "Smell of smoke in Kerry?" , "Smell, like a Kerry mountain?" .)