Allow client to reject odd elements
I believe the answer is:
let
'allow' is the definition.
(synonyms)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for let that I've seen before include "Rent out (property)" , "Reason for scrubbing service" , "Allow on the tennis court" , "Allow, don't hinder" , "Allow; rental period" .)