Moisture suspended in air (6)
I believe the answer is:
vapour
'moisture suspended in air' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for vapour that I've seen before include "Gaseous form of liquid substance" , "Gaseous state of matter" , "Visible steam or clouds" , "Substance diffused in the air" , "Airborne condensation" .)