Changed course after Ascot extremely harshly criticised (8)
I believe the answer is:
attacked
'harshly criticised' is the definition.
(attack can mean to criticise)
'changed course after ascot extremely' is the wordplay.
'changed course' becomes 'tacked' (as in changing tack).
'after' means one lot of letters go next to another.
'extremely' says to hollow out the word (remove centre letters) (only the extremes of the word are used).
'ascot' with its middle taken out is 'at'.
'tacked' put after 'at' is 'ATTACKED'.
(Other definitions for attacked that I've seen before include "Launched an assault" , "fired weapons" , "Roasted" , "Ambushed" , "Assailed, set upon" .)