Fight to send packing walker’s pack (8)

I believe the answer is:

rucksack

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'walker's pack' is the definition.
(I've seen this before)

'fight to send packing' is the wordplay.
'fight' becomes 'ruck' (I've seen this before).
'to send packing' becomes 'sack' (I can't justify this - if you can you should believe this answer much more).
'ruck'+'sack'='RUCKSACK'

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(Other definitions for rucksack that I've seen before include "Hiker often carries one on back" , "large bag" , "shoulder-bag" , "Trekker's baggage" , "Hiking bag" .)

I've seen this clue in The Times.

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