DJIA components (3)
I believe the answer is:
cos
'djia components' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for cos that I've seen before include "something of a salad" , "naturally having longer leaves than most" , "A long-leaved lettuce" , "in the Dodecanese?" , "Senior officers" .)