Stunning reason workers haven't been on track recently? (8)
I believe the answer is:
striking
I believe this is a double definition.
'stunning' is the first definition.
(I've seen this in another clue)
'reason workers haven't been on track recently?' is the second definition.
(as in train strikes)
(Other definitions for striking that I've seen before include "Remarkable; hitting" , "means of putting pressure on employers" , "Conspicuous" , "Delivering a blow" , "Impressive; refusing to work" .)