Dismissed heavy defeat with leader gone (3)
I believe the answer is:
out
'dismissed' is the definition.
(dismissed in cricket)
'heavy defeat with leader gone' is the wordplay.
'heavy defeat' becomes 'rout' (I've seen this before).
'with leader gone' means to remove the first letter.
'rout' with its initial letter removed is 'OUT'.
(Other definitions for out that I've seen before include "Away; into public domain" , "Openly gay" , "not acceptable" , "Away from home" , "In error" .)