Rocky ridge with ice is a killer (8)
I believe the answer is:
regicide
'killer' is the definition.
(regicide is a kind of killer)
'rocky ridge with ice' is the wordplay.
'rocky' is an anagram indicator.
'with' is a charade indicator (letters next to each other).
'ridge'+'ice'='ridgeice'
'ridgeice' with letters rearranged gives 'REGICIDE'.
'is a' acts as a link.
(Other definitions for regicide that I've seen before include "Killing monarch" , "Murder of a king" , "murder of top man" , "What Macbeth did" , "King-killer" .)