Lone arrangement with British peer (5)
I believe the answer is:
noble
'peer' is the definition.
(I've seen this in other clues)
'lone arrangement with british' is the wordplay.
'arrangement with' is an anagram indicator.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'lone' with its letters anagrammed with 'b' makes 'NOBLE'.
(Other definitions for noble that I've seen before include "Maybe count" , "gold coin, now obsolete" , "Illustrious - old money" , "Lord" , "Dignified" .)