We stand exposed, clutching the warning (6)
I believe the answer is:
beware
'the warning' is the definition.
('beware!' might be shouted as a warning)
'we stand exposed clutching' is the wordplay.
'stand' says the letters should be written in reverse (I've seen 'standing' mean this (in a down clue, letters stand up)).
'exposed' becomes 'bare' (I've seen this in other clues).
'clutching' means one lot of letters goes inside another.
'we' backwards is 'ew'.
'ew' going into 'bare' is 'BEWARE'.
(Other definitions for beware that I've seen before include "Be alert for dangers" , "Steer clear of" , "Look out, take care" , "Cry of warning" , "Archaic warning to be careful, danger ahead" .)