Edward is one barman in Ireland not fit to serve (8)
I believe the answer is:
inedible
'not fit to serve' is the definition.
I can't judge whether this definition defines the answer.
'edward is one barman in ireland' is the wordplay.
'edward' becomes 'ned'.
'is one' becomes 'i' ('i' can be a synonym of 'one').
'barman' becomes 'bl' (I can't explain this - if you can you should give a lot more credence to this answer).
'in' is an insertion indicator.
'ireland' becomes 'ie' (two letter country code).
'ned'+'i'+'bl'='nedibl'
'nedibl' inserted within 'ie' is 'INEDIBLE'.
Can you help me to learn more?
(Other definitions for inedible that I've seen before include "Not good as food" , "not course material?" , "not to be swallowed" , "needing to be taken off table?" , "Unfit for consumption" .)