Give evidence (4,7)
'give evidence' is the definition.
(thesaurus)
This is all the clue.
(Other definitions for bear witness that I've seen before include "Give testimony" , "Testify (to)" .)
'give evidence' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for testify that I've seen before include "Affirm (on oath)" , "sworn" , "Give evidence in court" , "Bear witness in court" , "take the stand" .)