Writer with name on flag (6)
I believe the answer is:
pennon
'flag' is the definition.
(pennon is a kind of flag)
'writer with name on' is the wordplay.
'writer with' becomes 'pen' (I've seen this in other clues).
'name' becomes 'n' (common abbreviation e.g. on forms).
'pen'+'n'+'on'='PENNON'
(Other definitions for pennon that I've seen before include "Narrow, swallow-tailed standard" , "Long narrow triangular flag" , "Flag carried by 9 across" , "Streamer on a lance" , "Knight's personal flag" .)