Recall working twice? An impossibility (2-2)
I believe the answer is:
no-no
'an impossibility' is the definition.
(I've seen this before)
'recall working twice?' is the wordplay.
'recall' says the letters should be written in reverse.
'working' becomes 'on' (on can mean working or activated).
'twice?' says to double the letters (I've seen 'twice' mean this).
'on' backwards is 'no'.
'no' duplicated is 'NO-NO'.
(Other definitions for no-no that I've seen before include "Something that would be totally unacceptable" , "Impossibility" , "Non-starter" , "Something that must not be done (informal)" , "Something totally unacceptable (informal)" .)