Improve on tea, say, with more of it: that's a test for humanity (7)
I believe the answer is:
captcha
'with more of it that's a test for humanity' is the definition.
I know nothing about this answer so I cannot judge whether this works.
'improve on tea' is the wordplay.
'improve on' becomes 'capt' (I can't justify this - if you can you should give a lot more credence to this answer).
'tea' becomes 'cha' (cha is a type of tea).
'capt'+'cha'='CAPTCHA'
'say' is the link.
Can you help me to learn more?
(Another definition for captcha that I've seen is " E-security feature".)