They fight with the others, having nasty looks, no heart (9)
I believe the answer is:
wrestlers
'they' is the definition.
Both the answer and definition are plural nouns.
Maybe they are linked in a way I don't understand?
'fight with the others having nasty looks no heart' is the wordplay.
I cannot quite see how this works, but
'with' could be 'w' (abbreviation) and 'w' is found in the answer.
'others' could be 'rest' (I've seen this before) and 'rest' is found within the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Another definition for wrestlers that I've seen is " Sumo types".)