One abroad loved touring northern plain (9)
I believe the answer is:
unadorned
'plain' is the definition.
(associated in meaning)
'one abroad loved touring northern' is the wordplay.
'one abroad' becomes 'un' (French for 'one' - when abroad).
'loved' becomes 'adored' (similar in meaning).
'touring' indicates putting letters inside (touring can mean going round).
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'adored' going around 'n' is 'adorned'.
'un'+'adorned'='UNADORNED'
(Other definitions for unadorned that I've seen before include "Not decorated, plain and simple" , "Simple and plain as around den" , "Without embellishment" , "Plain, undecorated" .)