Malaise caused by air travel (3,3)
I believe the answer is:
jet lag
'malaise caused by air travel' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for jet lag that I've seen before include "Effect of long distance journey" , "Post-flight exhaustion" , "Air traveller's tiredness" , "Malaise caused by air travel" , "Delayed tiredness after long plane journey" .)