There will be correspondence in this paper principally over street fight (7)

I believe the answer is:

postbox

I'm a little stuck... Click here to teach me more about this clue!

'there will be correspondence in this paper principally over street fight' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps they are linked in a way I don't understand?

'paper principally over street fight' is the wordplay.
'principally' says to take the initial letters.
'over' becomes 'o' (cricket abbreviation).
'street' becomes 'st' (abbreviation).
'fight' becomes 'box' (boxing is a kind of fighting).
The first letter of 'paper' is 'p'.
'p'+'o'+'st'+'box'='POSTBOX'

Can you help me to learn more?

(Other definitions for postbox that I've seen before include "Mail receptacle" , "Letter collector" , "Receptacle for 7" .)

I've seen this clue in The Independent.

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