Language I long to learn? (5)
I believe the answer is:
lingo
'language' is the definition.
(lingo is a kind of language)
'long to learn?' is the wordplay.
'long' becomes 'l'.
'to learn?' becomes 'ingo' (I can't justify this - if you can you should believe this answer much more).
'l'+'ingo'='LINGO'
'i' acts as a link.
This may not be right. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for lingo that I've seen before include "Language, colloquially speaking." , "Vernacular" , "Argot" , "Tongue" , "Jargon, language (colloq.)" .)