Fires again as rule before it ends heartlessly (9)

'fires again' is the definition.
Although both the answer and definition are verbs in their -s form, I cannot understand how one could define the other.

'rule before it ends heartlessly' is the wordplay.
'rule' becomes 'reign' (reign is a kind of rule).
'before' means one lot of letters go next to another.
'heartlessly' suggests removing the centre.
'ends' with its middle removed is 'es'.
'reign'+'it'+'es'='REIGNITES'

'as' is the link.

Can you help me to learn more?