Ensign on carrier is outstanding leader (8-6)
I believe the answer is:
standard-bearer
'outstanding leader' is the definition.
(I've seen this before)
'ensign on carrier' is the wordplay.
'ensign' becomes 'standard' (both can mean a flag).
'on' means one lot of letters go next to another (in a down clue, letters appear on others).
'carrier' becomes 'bearer' (synonyms).
'standard'+'bearer'='STANDARD-BEARER'
'is' is the link.
(Other definitions for standard-bearer that I've seen before include "Leading figure in a cause" , "Leading figure in a movement" , "Leader of a cause" , "Flag-carrying soldier" .)