Symbol of power not concerning one cold philosopher (7)
I believe the answer is:
Here is my best explanation:
'philosopher' is the definition.
(sceptic is a type of philosopher)
'symbol of power not concerning one cold' is the wordplay.
'symbol of power' becomes 'sceptre'.
'not' suggests deleting specific letters.
'concerning' becomes 're'.
'one' becomes 'i' (Roman numeral).
'cold' becomes 'c' (eg on taps).
'sceptre' with 're' removed is 'scept'.
(Other definitions for sceptic that I've seen before include "One who doubts the truth of religions", "Philosopher", "One who doubts accepted opinions", "I may doubt that", "One might doubt it", "Thomas for one", "One inclined to question accepted opinions", "One doesn't believe", "doubter" and "One habitually doubts accepted beliefs".)