Fainthearted (5)
I believe the answer is:
timid
'faint-hearted' is the definition.
(I know that faint-hearted can be written as timid)
This is all the clue.
(Other definitions for timid that I've seen before include "Mouse" , "Gutless" , "afraid to speak out?" , "Not brave" , "Not assertive, retiring" .)