One official language of Pakistan (4)
I believe the answer is:
urdu
'one official language of pakistan' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for urdu that I've seen before include "Sanskrit language" , "Language spoken by Moslems in Pakistan and India" , "Indian language" , "Language akin to Hindi" , "Sub-continental language" .)