Great memes in Twitch (7)
I believe the answer is:
immense
'great' is the definition.
(immense can mean great or huge)
'memes in twitch' is the wordplay.
'twitch' indicates an anagram (I've seen 'twitching' mean this (letters twitch or move into a new order)).
'memes'+'in'='memesin'
'memesin' anagrammed gives 'IMMENSE'.
(Other definitions for immense that I've seen before include "Vast or enormous" , "Very big, exceedingly great" , "Massive" , "Unusually large or great" , "Unctuously ingratiating" .)