Sailor with his chum a great deal (7)

I believe the answer is:

matelot

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'sailor' is the definition.
(I've seen this before)

'chum a great deal' is the wordplay.
'chum' becomes 'mate' (I've seen this in another clue).
'a great deal' becomes 'lot' (synonyms).
'mate'+'lot'='MATELOT'

'with his' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.

Can you help me to learn more?

(Other definitions for matelot that I've seen before include "Sailor (slang from French)" , "One at sea" , "One sailor" , "seafarer" , "Rating" .)

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