Nude sadly ordered to leave area at once (8)
I believe the answer is:
suddenly
'at once' is the definition.
'nude sadly ordered to leave area' is the wordplay.
I cannot quite understand how this works, but
'area' could be 'den' (den is a kind of area) and 'den' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for suddenly that I've seen before include "Unexpectedly, abruptly" , "Quickly, unexpectedly" , "Quickly and without warning" , "Out of the blue" , "In an unexpected manner" .)