Surprise electricity charge? (5)

I believe the answer is:

shock

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'surprise' is the definition.
(I know that shock is a type of surprise)

'electricity charge?' is the wordplay.
'electricity' becomes 's' (I can't justify this - if you can you should believe this answer much more).
'charge?' becomes 'hock' (hocking is a kind of charging).
's'+'hock'='SHOCK'

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(Other definitions for shock that I've seen before include "Horrify - stroke" , "Jar" , "Appal" , "Outrageous" , "Trauma" .)

I've seen this clue in the Evening Standard.

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