Chick egg, by the look of it, left in rain (5)
I believe the answer is:
owlet
'chick' is the definition.
(a young owl)
'it left in rain' is the wordplay.
'it' becomes 'o' (I can't explain this - if you can you should give a lot more credence to this answer).
'left' becomes 'l' (common abbreviation).
'in' is an insertion indicator.
'rain' becomes 'wet' (I've seen this in other clues).
'l' placed inside 'wet' is 'wlet'.
'o'+'wlet'='OWLET'
'egg by the look of' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
(Other definitions for owlet that I've seen before include "Towel (anag)" , "Young nocturnal bird of prey" , "Wise avian's youngster?" , "Offspring of the wise one?" , "Young bird of the night" .)