Get to part of waterway (5)

I believe the answer is:

reach

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'get to' is the definition.
(synonyms)

'part of waterway' is the wordplay.
'part' becomes 're' (re is a kind of part).
'of waterway' becomes 'ach' (I can't justify this - if you can you should believe this answer much more).
're'+'ach'='REACH'

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(Other definitions for reach that I've seen before include "Grasp" , "Hit" , "Stretch of river: achieve" , "Arrive at, attain" , "Limits within which something can be effective" .)

I've seen this clue in The Mirror.

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