Procedure ultimately no good — read out words of warning (2,5)
I believe the answer is:
en garde
'words of warning' is the definition.
(I've seen this before)
'procedure ultimately no good read out' is the wordplay.
'ultimately' indicates one should take the final letters.
'no good' becomes 'ng' (abbreviation).
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
The final letter of 'procedure' is 'e'.
'read' with letters rearranged gives 'arde'.
'e'+'ng'+'arde'='EN GARDE'
(Other definitions for en garde that I've seen before include "Words of warning" , "Prepare to fence!" , "(In fencing) in a defensive stance" , "Warning cry in fencing" , "The opening position in fencing - mind yourself" .)