Out of Sellotape now, all of a sudden (2,3,4,5)
I believe the answer is:
at one fell swoop
'all of a sudden' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.
'out of sellotape now' is the wordplay.
'out' indicates anagramming the letters.
'of'+'sellotape'+'now'='ofsellotapenow'
'ofsellotapenow' anagrammed gives 'AT ONE FELL SWOOP'.
Can you help me to learn more?
(Other definitions for at one fell swoop that I've seen before include "46 [AT THE SAME TIME]?" , "all together" .)