Waiting to get that wrapped up before taking the day off (2,3,5)
'waiting to get' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.
'wrapped up before taking the day off' is the wordplay.
'wrapped up' becomes 'atth' (I can't justify this - if you can you should give a lot more credence to this answer).
'before' becomes 'ere' (usually literary).
'taking' means one lot of letters go next to another.
'off' is an anagram indicator.
'day' anagrammed gives 'ady'.
'atth'+'ere'+'ady'='AT THE READY'
'that' acts as a link.
Can you help me to learn more?
(Other definitions for at the ready that I've seen before include "dipping hand in till?", "Prepared for instant action", "Prepared or available for immediate use", "Available for use in operating", "on standby".)