Simpletons so timid, having lost heart sadly (6)
I believe the answer is:
idiots
'simpletons' is the definition.
(idiot is a kind of simpleton)
I cannot understand how the rest of the clue works.
(Other definitions for idiots that I've seen before include "chumps" , "clowns?" , "Fools, air-heads" , "imbeciles" , "Foolish people" .)