Pagans do this to cold layers (8)
I believe the answer is:
heathens
'pagans' is the definition.
('heathen' can be a synonym of 'pagan')
'cold layers' is the wordplay.
'cold' becomes 'heat' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'layers' becomes 'hens' (hens lay eggs).
'heat'+'hens'='HEATHENS'
'do this to' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for heathens that I've seen before include "They don't believe in any of the major religions" , "Those who do not believe in the main religions" , "pagans" , "Athens he searched for non-believers" .)