Waiting for that to be resolved before the day is out (2,3,5)
I believe the answer is:
at the ready
'waiting' is the definition.
I know nothing about this answer so I cannot judge whether this works.
'that to be resolved before the day is out' is the wordplay.
'to be resolved' indicates anagramming the letters.
'before' becomes 'ere' (poetic term for 'before').
'is out' is an anagram indicator (I've seen 'was out' mean this).
'that' anagrammed gives 'atth'.
'day' with letters rearranged gives 'ady'.
'atth'+'ere'+'ady'='AT THE READY'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for at the ready that I've seen before include "Prepared or available for immediate use" , "Poised for action" , "Available for use in operating" , "on standby" , "dipping hand in till?" .)