Power cut? That's disgusting (4)
I believe the answer is:
phew
'that's disgusting' is the definition.
I can't judge whether this definition defines the answer.
'power cut?' is the wordplay.
'power' becomes 'p' (symbol in physics).
'cut?' becomes 'hew' (hew can mean to chop or cut).
'p'+'hew'='PHEW'
Can you help me to learn more?
(Other definitions for phew that I've seen before include "Expression of relief" , "Gosh, that's a relief!" , "Exclamation of relief" , "I'm overheating?" , "Good gracious, its hot!" .)