Engineer and his language (6)
I believe the answer is:
danish
'language' is the definition.
(I've seen this before)
'engineer and his' is the wordplay.
'engineer' is an anagram indicator.
'and'+'his'='andhis'
'andhis' with letters rearranged gives 'DANISH'.
(Other definitions for danish that I've seen before include "Relating to Denmark" , "Relating to one from Copenhagen, say" , "A blue cheese; a pastry" , "speech from Hamlet?" , "Hamlet's nationality" .)