Crown court imprisoning alternative individual (7)
I believe the answer is:
coronet
'crown' is the definition.
(coronet is a kind of crown)
'court imprisoning alternative individual' is the wordplay.
'court' becomes 'ct'.
'imprisoning' indicates putting letters inside.
'alternative' becomes 'or'.
'individual' becomes 'one'.
'or'+'one'='orone'
'ct' enclosing 'orone' is 'CORONET'.
(Other definitions for coronet that I've seen before include "Simple crown" , "emblem of rank" , "mark of noble rank?" , "Jewelled headgear for peer" , "Circular floral head decoration" .)