Yet three sevens turn out to be around fifty (12)
I believe the answer is:
nevertheless
'yet' is the definition.
(thesaurus)
'three sevens turn out to be around fifty' is the subsidiary indication.
'turn out' indicates an anagram.
'to be around' means one lot of letters goes inside another.
'fifty' becomes 'l' ('l' can be a synonym of 'fifty').
'three'+'sevens'='threesevens'
'threesevens' anagrammed gives 'nevertheess'.
'nevertheess' going around 'l' is 'nevertheless'.
(Other definitions for nevertheless that I've seen before include "In spite of everything" , "But always" , "Notwithstanding" , "anyhow" , "However" .)