Chronicles concerned with trousers (7)
I believe the answer is:
records
'chronicles' is the definition.
'concerned with trousers' is the wordplay.
'concerned with' becomes 're'.
'trousers' becomes 'cords' (cords is a kind of trousers).
're'+'cords'='RECORDS'
(Other definitions for records that I've seen before include "unsurpassed performances" , "Annotations of events" , "Discs" , "Files" , "Makes written note" .)