Showing heart, cross about conflict, one trained to attack (6,7)

'showing heart' is the definition.
The definition suggests a singular noun which matches the answer.

'cross about conflict one trained to attack' is the wordplay.
I cannot quite understand how this works, but
'cross' could be 't' (shape) and 't' is present in the answer.
'about' could be 're' ('re' means regarding or about) and 're' is found within the answer.
'conflict' could be 'war' (war is a kind of conflict) and 'war' is present in the answer.
'to' could be 'for' and 'for' is present in the answer.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?