Five diamonds causing wickedness (4)
I believe the answer is:
vice
'wickedness' is the definition.
(I've seen this in another clue)
'five diamonds' is the wordplay.
'five' becomes 'V' (Roman numeral).
'diamonds' becomes 'ice' (slang term for diamonds).
'v'+'ice'='VICE'
'causing' acts as a link.
(Other definitions for vice that I've seen before include "As a substitute for; immoral behaviour" , "In place of - depravity" , "Is the gripping tool evil?" , "perversion" , "Sin; weakness" .)