A silly or contemptible person (5)
I believe the answer is:
twerp
This clue is a double definition.
'a silly' is the first definition.
(I've seen this before)
'contemptible person' is the second definition.
(I've seen this before)
(Other definitions for twerp that I've seen before include "Foolish person (slang)" , "ass" , "Ninny" , "Foolish fellow" , "Silly person" .)