Thing puncturing another – one's lighter (7)
I believe the answer is:
impaler
'thing puncturing another' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'one's lighter' is the wordplay.
'one's' becomes 'I'm' ('one is' is a formal way of saying 'I am').
'lighter' becomes 'paler' ('pale' can be similar in meaning to 'light').
'im'+'paler'='IMPALER'
Can you help me to learn more?
(Another definition for impaler that I've seen is " murderous stakeholder".)