Communicate what errors do? (3,6)
I believe the answer is:
get across
'communicate' is the definition.
(I've seen this in another clue)
I cannot understand how the remainder of the clue works.
(Other definitions for get across that I've seen before include "Clearly explain" , "Go over - explain" , "Express" , "what crucifer must do first of all" , "go over viaduct, say" .)