Flasher shocking South Leigh (10)
I believe the answer is:
lighthouse
'flasher' is the definition.
(something which flashes)
'shocking south leigh' is the wordplay.
'shocking' is an anagram indicator (I've seen this in other clues).
'south'+'leigh'='southleigh'
'southleigh' with letters rearranged gives 'LIGHTHOUSE'.
(Other definitions for lighthouse that I've seen before include "Beamer" , "Tall structure emitting flashes to guide ships" , "it sends a warning" , "tower" , "Warning feature for shipping" .)