Mythic vessel received by leaderless mystical sect (5,4)

'sect' is the definition.

'mythic vessel received by leaderless mystical' is the wordplay.
'mythic vessel' becomes 'argo' (ship in Greek mythology).
'received by' indicates putting letters inside.
'leaderless' means to remove the first letter.
'mystical' becomes 'occult' (I've seen this before).
'occult' with its initial letter taken off is 'ccult'.
'argo' inserted into 'ccult' is 'CARGO CULT'.