He's familiar also with a Yankee (4)
I believe the answer is:
andy
'he's familiar' is the definition.
The definition suggests a singular noun which matches the answer.
'also with a yankee' is the wordplay.
'also' becomes 'and' (both can mean in addition).
'with' says to put letters next to each other.
'a yankee' becomes 'Y' (phonetic alphabet: alpha, bravo, charlie etc.).
'and'+'y'='ANDY'
Can you help me to learn more?
(Other definitions for andy that I've seen before include "- - Warhol (art)" , "Man" , "Andrew (dim.)" , "-- Capp, cartoon layabout" , "Chap" .)