Shock as king's admitted to lack of power (7)
I believe the answer is:
outrage
'shock' is the definition.
(I know that shock can be written as outrage)
'king's admitted to lack of power' is the wordplay.
'king' becomes 'R' (abbreviation for rex, king in Latin).
'admitted to' indicates putting letters inside.
'lack of power' becomes 'outage' (I've seen this in another clue).
'r' inserted into 'outage' is 'OUTRAGE'.
'as' acts as a link.
(Other definitions for outrage that I've seen before include "Fury" , "Deplorable insult" , "scandalous!" , "Strong reaction of anger or indignation" , "Atrocious act" .)