How heat might cause damage to half of fresco church displayed (6)
I believe the answer is:
scorch
'how heat' is the definition.
'scorch' can be an answer for 'heat' (scorching is a kind of heating). I am not sure about the 'how' bit.
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for scorch that I've seen before include "Burn lightly" , "Burn; drive very fast (informal)" , "Wither from exposure to heat" , "Shrivel through heat" , "dry up" .)