Misfortune sees Sid losing head, in a manner of speaking (8)
I believe the answer is:
accident
'misfortune' is the definition.
(accident is a kind of misfortune)
'sid losing head in a manner of speaking' is the wordplay.
'losing head' means to remove the first letter.
'in' is an insertion indicator.
'a manner of speaking' becomes 'accent' (accent is a kind of manner of speaking).
'sid' with its initial letter taken away is 'id'.
'id' placed inside 'accent' is 'ACCIDENT'.
'sees' acts as a link.
(Other definitions for accident that I've seen before include "Prang" , "Eg, car crash" , "Calamity" , "Chance misfortune or injury" , "Contretemps" .)