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 subsidiary indication.
'fellow' becomes 'co' (I've seen this in other clues).
'protege' becomes 'ward'.
'extremely' suggests removing the centre.
'lazy' with its middle removed 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".)