Number one repeated, afraid last on card essential for bingo! (6,6,7,6)

'card essential for bingo' is the definition.
I don't know anything about this answer so I cannot judge whether this works.

'number one repeated afraid last' is the wordplay.
I cannot quite understand how this works, but
'number' could be 'k' (K is an example) and 'k' is found in the answer.
'one' could be 'i' (Roman numeral) and 'i' is located in the answer.
'last' could be 'end' (I've seen this in another clue) and 'end' is located in the answer.
This may be the basis of the clue (or it may be nonsense).

'on' acts as a link.

Can you help me to learn more?