Sharp turn (3)
'sharp turn' is the definition.
(I've seen this in another clue)
This is all the clue.
I believe this is a double definition.
'sharp' is the first definition.
(thesaurus)
'turn' is the second definition.
(sheering is a kind of turning)
(Other definitions for sheer that I've seen before include "Absolutely - diaphanous" , "Complete" , "Deviate (from) - vertical" , "Utter - precipitous" , "Gossamer or precipitous" .)