Mark a record for language (7)
I believe the answer is:
tagalog
'language' is the definition.
(Tagalog is an example)
'mark a record' is the wordplay.
'mark' becomes 'tag' (tag is a kind of mark).
'record' becomes 'log' (logging is a kind of recording).
'tag'+'a'+'log'='TAGALOG'
'for' acts as a link.
(Other definitions for tagalog that I've seen before include "Asian language" , "people in the Philippines" , "Pacific islander" .)