Apparently an off-day for twelve (7)
I believe the answer is:
noonday
'apparently an off-day for twelve' is the definition.
I can't tell whether this defines the answer.
'day for twelve' is the wordplay.
'for' says to put letters next to each other (I've seen this in other clues).
'twelve' becomes 'noon' (twelve noon).
'day' put after 'noon' is 'NOONDAY'.
Can you help me to learn more?
(Other definitions for noonday that I've seen before include "Time when the sun is highest" , "When the sun's at its highest point" , "time of greatest prosperity" , "12 o'clock" , "Midday, 12p.m." .)