Leave home carrying penny metal fastener (5,3)

I believe the answer is:

split pin

'metal fastener' is the definition.
(item which fastens things)

'leave home carrying penny' is the wordplay.
'leave' becomes 'split' (I've seen this before).
'home' becomes 'in' ('he's home' can mean 'he's in').
'carrying' means one lot of letters go next to another (in a down clue, the bottom letters carry others).
'penny' becomes 'p' (short for pence).
'in' after 'p' is 'pin'.
'split'+'pin'='SPLIT PIN'

I've seen this clue in The Guardian.

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