Language curve takes a big cut (6)
I believe the answer is:
arabic
'language' is the definition.
(Arabic is an example)
'curve takes a big cut' is the wordplay.
'curve' becomes 'arc' (arc is a kind of curve).
'takes' indicates putting letters inside.
'cut' means to remove the last letter.
'a'+'big'='abig'
'abig' with its last letter taken away is 'abi'.
'arc' enclosing 'abi' is 'ARABIC'.
(Other definitions for arabic that I've seen before include "Language of North Africa and the Middle East" , "Gum --, ingredient of glue and incense" , "Middle Eastern language" , "Final" , "Language (by gum!)" .)