Half dead except at the start (5)
I believe the answer is:
debut
'the start' is the definition.
(debut is a kind of start)
'half dead except' is the wordplay.
'half' indicates taking half.
'except' becomes 'but' (I've seen this in another clue).
'dead' cut in half is 'de'.
'de'+'but'='DEBUT'
'at' is the link.
(Other definitions for debut that I've seen before include "The coming out of a society girl" , "Tubed (anag.)" , "First appearance in society" , "First appearance, a coming-out" , "where one began" .)