Fellow protege, extremely lazy and faint-hearted (8)
I believe the answer is:
Here is my best explanation:
'faint-hearted' is the definition.
'fellow protege extremely lazy' is the wordplay.
'fellow' becomes 'co' (I've seen this in other clues**).
'protege' becomes 'ward'.
'extremely' suggests removing the centre.
'lazy' with its middle taken out is 'ly'.
'and' is the link.
(Other definitions for cowardly that I've seen before include "Lily-livered", "Faint-hearted", "Lacking courage", "Yellow", "lacking courage", "chicken" and "yellow".)