Copper with headgear covering cold skin (7)
I believe the answer is:
cuticle
'skin' is the definition.
(I know that cuticle is a type of skin)
'copper with headgear covering cold' is the wordplay.
'copper' becomes 'Cu' (Cu is the chemical symbol for copper).
'with' means one lot of letters go next to another.
'headgear' becomes 'tile' (old-fashioned term for a hat).
'covering' means one lot of letters goes inside another.
'cold' becomes 'c' (eg on taps).
'tile' placed around 'c' is 'ticle'.
'cu'+'ticle'='CUTICLE'
(Other definitions for cuticle that I've seen before include "Dead skin at the base of a fingernail" , "Skin around the nail" , "Skin at foot of nail" , "layer of protection" , "Ice cult? (anag)" .)