Sulk about crew backing blackout (5,3)
I believe the answer is:
power cut
'blackout' is the definition.
(I've seen this before)
'sulk about crew backing' is the wordplay.
'sulk' becomes 'pout' (synonyms).
'about' means one lot of letters goes inside another.
'backing' says the letters should be written in reverse.
'crew' reversed gives 'werc'.
'pout' enclosing 'werc' is 'POWER CUT'.
(Other definitions for power cut that I've seen before include "black out" , "Go-getter's hairstyle" , "blackout" , "Interruption in electricity supply" , "Failure" .)