Lip turned grey - effect of heat, you see (6)
I believe the answer is:
mirage
'effect of heat you see' is the definition.
I can't tell whether this definition defines the answer.
'lip turned grey' is the wordplay.
'lip' becomes 'rim' (synonyms).
'turned' shows that the letters should be reversed in order.
'grey' becomes 'age' (I've seen this in another clue).
'rim' written backwards gives 'mir'.
'mir'+'age'='MIRAGE'
Can you help me to learn more?
(Other definitions for mirage that I've seen before include "French flier" , "Optical illusion caused by atmospheric conditions" , "fighter craft" , "French fighter aircraft" , "Illusions in the desert" .)