Greek god sat for artist, covering one leg (8)
I believe the answer is:
poseidon
'greek god' is the definition.
(Poseidon is an example)
'sat for artist covering one leg' is the wordplay.
'sat for artist' becomes 'posed' (I've seen this before).
'covering' is an insertion indicator.
'one' becomes 'i' (Roman numeral).
'leg' becomes 'on' (cricket term, fielding positions).
'posed' going around 'i' is 'poseid'.
'poseid'+'on'='POSEIDON'
(Other definitions for poseidon that I've seen before include "Sea Lord" , "underwater missile" , "associated with adventure on screen" , "Olympian" , "I snooped to find Greek god of the sea" .)