Tycoon in mood, glumly rejecting every other one (5)
I believe the answer is:
mogul
'tycoon' is the definition.
(both can mean a rich person)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for mogul that I've seen before include "Very wealthy or powerful business person" , "Powerful man" , "Bashaw" , "Magnate; mound of hard snow on a ski slope" , "Tycoon -- ski slope mound" .)