One might pick this rugby forward (4)

I believe the answer is:

lock

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'rugby forward' is the definition.
(lock is an example)

I cannot understand how the remainder of the clue works.

(Other definitions for lock that I've seen before include "element in pack" , "Stop moving" , "Fastening device" , "Tress of hair" , "Strand of hair" .)

I've seen this clue in The Independent.

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