Lone arrangement about British peer (5)
I believe the answer is:
noble
'peer' is the definition.
(I've seen this in another clue)
'lone arrangement about british' is the wordplay.
'arrangement' is an anagram indicator.
'about' indicates putting letters inside.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'lone' is an anagram of 'nole'.
'nole' enclosing 'b' is 'NOBLE'.
(Other definitions for noble that I've seen before include "Lord" , "Possibly count" , "gold coin, now obsolete" , "eg Earl" , "Having high moral qualities" .)