Monorail late as everyone's hiding on edge (3,2,4)
I believe the answer is:
ill at ease
'on edge' is the definition.
(I've seen this before)
'monorail late as everyone's hiding' is the wordplay.
'hiding' indicates the answer is hidden within the clue.
'ILL-AT-EASE' can be found hidden inside 'monorail late as everyones'.
(Other definitions for ill at ease that I've seen before include "wound up" , "Uncomfortable with a situation" , "Elite, alas? (Anag)" , "Fidgety" , "Unable to relax" .)