Nerd's language not right (4)
I believe the answer is:
geek
'nerd's' is the definition.
(I've seen this before)
'language not right' is the wordplay.
'language' becomes 'greek' (Greek is an example).
'not' indicates named letters should be taken away.
'right' becomes 'r' (common abbreviation).
'greek' with 'r' taken away is 'GEEK'.
(Other definitions for geek that I've seen before include "social misfit" , "PC expert?" , "Creep; misfit (sl.)" , "Socially inept person" , "Obsessive enthusiast" .)