Heat is reduced to around zero in US lake (5)
I believe the answer is:
tahoe
'us lake' is the definition.
(I've seen this before)
'heat is reduced to around zero' is the wordplay.
'is reduced' is an anagram indicator.
'to around' means one lot of letters goes inside another.
'zero' becomes 'O' (O resembles 0).
'heat' is an anagram of 'tahe'.
'tahe' going around 'o' is 'TAHOE'.
'in' acts as a link.
(Other definitions for tahoe that I've seen before include "Nevada/California lake" , "Mountain lake" , "US lake" , "the Nevada/California border area" , "Lake/desert resort on the California-Nevada border" .)