Eleventh-hour hold up, with day getting long (4-5)
I believe the answer is:
last-ditch
'eleventh-hour' is the definition.
(both can mean done at the last possible moment)
'hold up with day getting long' is the wordplay.
'hold up' becomes 'last' (synonyms).
'with' means one lot of letters go next to another.
'day' becomes 'd' (abbreviation for day).
'getting' says to put letters next to each other.
'long' becomes 'itch' (to long or itch for something is to desire it).
'last'+'d'+'itch'='LAST-DITCH'
(Other definitions for last-ditch that I've seen before include "Stitch lad up in final defence" , "Of an attempt or stand, final and desperate" , "Denoting final attempt (to do something)" , "Final recourse" , "Eleventh hour" .)