The ice might be starting to melt here but it's very cold at the cape (8,5)
I believe the answer is:
freezing point
'the ice might be starting to melt here but it's' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'cold at the cape' is the wordplay.
'cold' becomes 'freezing' (similar in meaning).
'at' means one lot of letters go next to another.
'the cape' becomes 'point' (both can mean a piece of land jutting into the sea).
'freezing'+'point'='FREEZING-POINT'
'very' acts as a link.
Can you help me to learn more?
(Other definitions for freezing point that I've seen before include "32F (of water)" , "Temperature at which a liquid solidifies" , "32F / 0C" , "Temperature of liquid/solid transition" , "(For water) 0oC" .)