Some off-colour, dull khaki comes from here (4)
I believe the answer is:
urdu
'khaki comes from here' is the definition.
(the word 'khaki' comes from the Urdu language)
'some off-colour dull' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'URDU' can be found hidden inside 'off colour dull'.
(Other definitions for urdu that I've seen before include "Pakistani language" , "Sub-continental language" , "Indian language" , "Indic language written in Persian script" , "Official language used in Pakistan" .)