What may separate ice from sole or similar fish (5)
I believe the answer is:
skate
This might be a double definition.
'what may separate ice from sole' is the first definition.
(an ice skate separates feet from ice)
'similar fish' is the second definition.
'skate' can be an answer for 'fish' (skate is a kind of fish). I am not sure about the 'similar' bit.
'or' acts as a link.
(Other definitions for skate that I've seen before include "Type of ray" , "A ray; slide smoothly" , "Lasso" , "Glide like large fish" , "Edible marine fish" .)