### Clue: Power mindless Republican held, looking back, is worry (7)
### Answer: PERTURB 
 ### Explanation: Definition: worry
  P(symbol for "power" in physics) + **reversal of**(…, looking back) [BRUTE(mindless/savage) **containing**(… held) R(abbrev. for member of the US Republican party)].
Another relevant surface – and he's still holding power.