Legal statement by Welby, maybe as a precaution (4,2,4)
I believe the answer is:
just in case
'as a precaution' is the definition.
(I've seen this before)
'legal statement by welby maybe' is the wordplay.
'legal statement' becomes 'case'.
'by' is a charade indicator (letters next to each other).
'welby maybe' becomes 'justin' (Archbishop of Canterbury Justin Welby).
'case' after 'justin' is 'JUST IN CASE'.
(Other definitions for just in case that I've seen before include "In the unlikely event of problems" , "as a precaution" , "Lest" , "For insurance" , "the judge needs to be" .)