Neither fellow made a conquest (6)
I believe the answer is:
norman
'a conquest' is the definition.
(Norman Conquest is an example)
'neither fellow' is the wordplay.
'neither' becomes 'nor' (eg in the phrase 'neither do I').
'fellow' becomes 'man' (fellow can mean a man).
'nor'+'man'='NORMAN'
'made' acts as a link.
(Other definitions for norman that I've seen before include "he invaded England" , "- Mailer, US author" , "1066 invader" , "Style of architecture" , "Person from France" .)