Unfriendly, but not really heated (4)
I believe the answer is:
cool
'unfriendly' is the definition.
(synonyms)
'not really heated' is the wordplay.
I cannot really understand how this works, but
'not' could be 'o' (I've seen this in other clues) and 'o' is found within the answer.
The remaining letters 'col' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'but' is the link.
Can you help me to learn more?
(Other definitions for cool that I've seen before include "Casual and confident - not heated" , "Calm; chilly" , "At fairly low temperature" , "Calm; not warm" , "Unemotional; excellent" .)