Distinguished archbishop is revolutionary (6)
I believe the answer is:
signal
'distinguished' is the definition.
(thesaurus)
'archbishop is revolutionary' is the wordplay.
'archbishop' becomes 'lang' (Cosmo Gordon Lang, Archbishop of Canterbury).
'revolutionary' is a reversal indicator.
'lang'+'is'='langis'
'langis' written backwards gives 'SIGNAL'.
(Other definitions for signal that I've seen before include "way to communicate" , "Communication with encoded message" , "Striking; gesture" , "Not noise" , "Gesture giving information or command" .)