Base of British Legion abroad (7)
I believe the answer is:
ignoble
'base' is the definition.
('ignoble' can be similar in meaning to 'base')
'british legion abroad' is the wordplay.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'abroad' indicates an anagram.
'b'+'legion'='blegion'
'blegion' anagrammed gives 'IGNOBLE'.
'of' is the link.
(Other definitions for ignoble that I've seen before include "Completely lacking in character or purpose" , "'Base, dishonourable (7)'" , "Not worthy in character or purpose" , "No bilge! (anag)" , "Cheap" .)