Erring like a salver (6)
I believe the answer is:
astray
'erring' is the definition.
(I've seen this in another clue)
'like a salver' is the wordplay.
'like' becomes 'as'.
'a salver' becomes 'tray' (I've seen this before).
'as'+'tray'='ASTRAY'
(Other definitions for astray that I've seen before include "Wandering off the path" , "Like carrier" , "Gone off the right path" , "Well off course" , "(Gone) in wrong direction" .)