Top one with murder conviction finally (5)
I believe the answer is:
crown
'top' is the definition.
(crown is a kind of top)
'one with murder conviction finally' is the wordplay.
'one with murder' becomes 'crow' (murder is the collective noun for crow).
'finally' indicates one should take the final letters.
The last letter of 'conviction' is 'n'.
'crow'+'n'='CROWN'
(Other definitions for crown that I've seen before include "Visible part of a tooth" , "sporting award" , "Headdress, coin" , "The sovereign" , "repair for damaged tooth" .)