Find those two endlessly at it and filter half of it out on online forum (7)
I believe the answer is:
'find those two endlessly at it' is the definition.
I can't tell whether this definition defines the answer.
'filter half of it out on online forum' is the wordplay.
'half of it' indicates taking half.
'out' indicates putting letters inside.
'on online forum' becomes 'witt' (I can't explain this - if you can you should believe this answer much more).
'filter' with half the letters taken is 'ter'.
'ter' enclosing 'witt' is 'TWITTER'.
'and' acts as a link.
Can you help me to learn more?
(Other definitions for twitter that I've seen before include "Social media provider" , "state of excitement" , "Chatter" , "Bird's sound; trivial talk" , "Chirping (could be electronic!)" .)