Warm enough to navigate fierce English rips (3-4)
I believe the answer is:
ice-free
'warm enough to navigate' is the definition.
'fierce english rips' is the wordplay.
'english' becomes 'e' (abbreviation).
'rips' indicates an anagram ('rip up' the original order of the letters).
'fierce'+'e'='fiercee'
'fiercee' is an anagram of 'ICE-FREE'.
(Other definitions for ice-free that I've seen before include "(Of water) not frozen" , "Like much of the Arctic in summer" .)