Justify being very mean (9)
I believe the answer is:
vindicate
'justify' is the definition.
(I know that justify can be written as vindicate)
'very mean' is the wordplay.
'very' becomes 'v' (abbreviation).
'mean' becomes 'indicate'.
'v'+'indicate'='VINDICATE'
'being' acts as a link.
(Other definitions for vindicate that I've seen before include "Make good a claim" , "Clear of blame" , "Justify by evidence or results" , "Avenge or exonerate" , "Deflect criticism" .)