Peninsula: sea freezing cold (5)
I believe the answer is:
medoc
'peninsula' is the definition.
I know nothing about this answer so I cannot judge whether this works.
'sea freezing cold' is the wordplay.
I cannot really see how this works, but
'sea' could be 'med' (abbreviation of Mediterranean) and 'med' is found in the answer.
'freezing' could be 'oc' (zero degrees Celsius) and 'oc' is found in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for medoc that I've seen before include "Wine-growing area" , "region of France" , "Type of wine" , "that's regularly drunk?" , "Red wine from southwest France" .)