Supports career employed by Building Society (6)
I believe the answer is:
braces
'supports' is the definition.
(I know this)
'career employed by building society' is the wordplay.
'career' becomes 'race' (career can mean to race around).
'employed by' indicates putting letters inside (inserted letters used or employed inside).
'building society' becomes 'BS' (abbreviation for building society).
'race' going into 'bs' is 'BRACES'.
(Other definitions for braces that I've seen before include "Couples" , "Straps used to keep trousers up" , "straps to hold your trousers up" , "Dental appliances and pairs" , "Straps holding up trousers" .)