Leg broken before morning light? (5)
I believe the answer is:
gleam
'light?' is the definition.
(I have seen 'brief light' mean 'gleam' so perhaps 'light' could also mean 'gleam')
'leg broken before morning' is the wordplay.
'broken' indicates an anagram.
'before' is a charade indicator (letters next to each other).
'morning' becomes 'am' (as in 12:00 AM).
'leg' is an anagram of 'gle'.
'gle'+'am'='GLEAM'
(Other definitions for gleam that I've seen before include "Glint" , "Ray" , "Glisten" , "Brief bright light" , "Sparkle, glimmer" .)