A broken antler the Norman leader used for a light (7)
I believe the answer is:
lantern
'for a light' is the definition.
(lantern is a type of light)
'a broken antler the norman leader' is the wordplay.
'a broken' indicates an anagram.
'leader' indicates taking the first letters.
The initial letter of 'norman' is 'n'.
'antler' with letters rearranged gives 'lanter'.
'lanter'+'n'='LANTERN'
'used' is the link.
(Other definitions for lantern that I've seen before include "outside D [DECORATION]" , "Enclosed light" , "Top of lighthouse" , "Encased light" , "Type of lamp" .)