Silly person (3)
'silly person' is the definition.
(twerp can mean a silly or annoying person)
This is the entire clue.
(Other definitions for twerp that I've seen before include "mug" , "Nincompoop" , "Nitwit" , "Foolish fellow" , "Fool" .)
'silly person' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for twit that I've seen before include "Twerp" , "Silly person; tease" , "Stupid person" , "Blockhead" , "Tease - fool" .)
(Other definitions for sap that I've seen before include "Undermine; fool" , "Insidiously undermine" , "The juice in trees" , "Tree's blood" , "Deplete, drain of resources" .)