Leave extremely dire role (6)
I believe the answer is:
depart
'leave' is the definition.
(synonyms)
'extremely dire role' is the wordplay.
'extremely' means to remove the middle letters (only the extremes of the word are used).
'role' becomes 'part' (eg a part or role in a film).
'dire' with its middle removed is 'de'.
'de'+'part'='DEPART'
(Other definitions for depart that I've seen before include "Go away; deviate" , "make tracks" , "Make an exit" , "Start out" , "Retire from" .)