Cowards at heart showing great fight (3)
I believe the answer is:
war
'great fight' is the definition.
'war' can be an answer for 'fight' (I've seen this in another clue). I am not sure about the 'great' bit.
'cowards at heart' is the wordplay.
'at heart' indicates the answer is hidden within the clue (letters hidden in the heart of the clue).
'WAR' is hidden in the letters of 'cowards'.
'showing' is the link.
Can you help me to learn more?
(Other definitions for war that I've seen before include "series of engagements" , "Armed hostility" , "Battle" , "Sustained conflict" , "Combat" .)