What's behind strange power cut? (4)
I believe the answer is:
rump
'what's behind' is the definition.
('rump' can be a synonym of 'behind')
'strange power cut?' is the wordplay.
'strange' becomes 'rum' (I've seen this before).
'power' becomes 'pe' (P.E. is an example).
'cut?' means to remove the last letter (I've seen 'cut' mean this).
'pe' with its final letter taken off is 'p'.
'rum'+'p'='RUMP'
(Other definitions for rump that I've seen before include "Rear; buttocks" , "Meat (from behind?)" , "Backside" , "Restricted parliament" , "Tail end" .)