Single file reveals just half of how ark was filled (8)

'how ark was filled' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.

'single file reveals just half' is the wordplay.
I cannot quite understand how this works, but
'single' could be 'one' (a single thing - only one) and 'one' is found within the answer.
'half' could be 'one' (I have seen 'Half of two ' mean 'one' so perhaps 'half' could also mean 'one') and 'one' is found in the answer.
The remaining letters 'by' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).

'of' acts as a link.

Can you help me to learn more?