Roman poet, half-cut, gambles on hard legendary king (9)

'legendary king' is the definition.
The definition suggests a singular noun which matches the answer.

'roman poet half-cut gambles on hard' is the wordplay.
'roman poet' becomes 'virgil'.
'half cut' means to take half the letters.
'gambles' becomes 'games' (I've seen this in another clue).
'on' says to put letters next to each other (in a down clue, letters appear on others).
'hard' becomes 'h' (abbreviation used in pencil classifications).
'virgil' cut in half is 'gil'.
'gil'+'games'+'h'='GILGAMESH'

Can you help me to learn more?