Crossword Genius

Soccer side, London one, second to take lead, one dealing heavy blow (5,6)

Ross

I believe the answer is:

steam hammer

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'soccer side london one second to take lead one' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.

'dealing heavy blow' is the wordplay.
'dealing heavy' becomes 'steam' (I can't explain this - if you can you should believe this answer much more).
'blow' becomes 'hammer' (hammer is a kind of blow).
'steam'+'hammer'='STEAM-HAMMER'

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I've seen this clue in The Independent.
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