Goes astray badly in outer Serbia (4)

I believe the answer is:

errs

I'm a little stuck... Click here to teach me more about this clue!

'goes astray' is the definition.
(I've seen this before)

I can't explain the remainder of the clue.

(Other definitions for errs that I've seen before include "Goes astray" , "Strays" , "Boobs" , "Is mistaken" , "Goes wrong" .)

I've seen this clue in the Evening Standard.

Want a hint initially instead of a full solution? Install my app