For us (3)
I believe the answer is:
our
'for us' is the definition.
('our' means belonging to us)
This is all the clue.
(Other definitions for our that I've seen before include "group possession?" , "''Now is the winter of ... discontent'' (Richard III)" , "Yours and mine" , "'-- House' (Madness song)" , "Belonging to us" .)