One of those (4)
I believe the answer is:
that
'one of those' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for that that I've seen before include "Yon" , "Take ..., English pop band" , "Not 8 Ac but the other" , "See 5" , "Just like --; -- is to say" .)