Arranged that before daybreak it would be lined up (2,3,5)
I believe the answer is:
at the ready
'it would be lined up' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'arranged that before daybreak' is the wordplay.
'arranged' indicates anagramming the letters.
'before' becomes 'ere' (poetic term for 'before').
'daybreak' becomes 'ady' (ady is day anagrammed 'broken').
'that' with letters rearranged gives 'atth'.
'atth'+'ere'+'ady'='AT THE READY'
Can you help me to learn more?
(Other definitions for at the ready that I've seen before include "Available for use in operating" , "on standby" , "Prepared or available for immediate use" , "Poised for action" , "dipping hand in till?" .)