Shaver's strangely gone rusty (9)
I believe the answer is:
youngster
'shaver's' is the definition.
(synonyms)
'strangely gone rusty' is the wordplay.
'strangely' indicates anagramming the letters.
'gone'+'rusty'='gonerusty'
'gonerusty' with letters rearranged gives 'YOUNGSTER'.
(Other definitions for youngster that I've seen before include "tyke" , "Stripling" , "Kid" , "Person of tender years" , "Rug rat in New York" .)