Crossword Genius

Rudder's astern, as it may be on a packet (6,7)

Ross

I believe the answer is:

return address

'on a packet' is the definition.
(a return address is often on a packet)

'rudder's astern as it may be' is the wordplay.
'as it may be' indicates anagramming the letters.
'rudders'+'astern'='ruddersastern'
'ruddersastern' is an anagram of 'RETURN ADDRESS'.

I've seen this clue in The Guardian.
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