Unpleasant thing to hear what Icarus thought shortly before crashing? (7)
I believe the answer is:
eyesore
'unpleasant thing' is the definition.
(something unpleasant to look at)
'thought shortly before crashing?' is the wordplay.
'thought' becomes 'eyes' (eyes is a kind of thought).
'shortly' means to remove the last letter.
'before crashing?' becomes 'sore' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'eyes' with its final letter taken off is 'eye'.
'eye'+'sore'='EYESORE'
'to hear what icarus' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.
(Other definitions for eyesore that I've seen before include "something one wouldn't want to see" , "Something ugly to look at" , "Ugly item" , "Something exceedingly ugly" , "bad sight" .)