Certify (with ‘for') (5)
I believe the answer is:
vouch
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">certify with for</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for vouch that I've seen before include "Declare support" , "Testify" , "warrant" , "Give personal assurance; guarantee" , "Be surety (for)" .)