Cross namely involving Judas (5)
I believe the answer is:
irate
'cross' is the definition.
(both can mean angry)
'namely involving judas' is the wordplay.
'namely' becomes 'ie' (short for 'id est', 'that is' in Latin).
'involving' is an insertion indicator.
'judas' becomes 'rat' (Judas can mean a traitor or rat).
'ie' placed around 'rat' is 'IRATE'.
(Other definitions for irate that I've seen before include "Magical rod" , "Livid" , "Angry and incensed" , "Boiling" , "having got in wax" .)