Attack instead of going on a voyage? (6)

I believe the answer is:

assail

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'attack' is the definition.
(synonyms)

'instead of going on a voyage?' is the wordplay.
'instead of' becomes 'as' (I can't explain this - if you can you should believe this answer much more).
'going on' says to put letters next to each other.
'a voyage?' becomes 'sail' (sail is a kind of voyage).
'as'+'sail'='ASSAIL'

Can you help me to learn more?

(Other definitions for assail that I've seen before include "Go for" , "Trouble" , "Set upon" , "Attack violently and persistently" , "Criticise severely" .)

I've seen this clue in the Evening Standard.

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