Join a male chum harvesting seaweed (10)
I believe the answer is:
amalgamate
'join' is the definition.
(I've seen this before)
'a male chum harvesting seaweed' is the wordplay.
I cannot quite understand how this works, but
'a' is within the answer.
'male' could be 'al' (shortened version of Alex or Alistair) and 'al' is located in the answer.
'chum' could be 'mate' (I've seen this before) and 'mate' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for amalgamate that I've seen before include "Join" , "Mix" , "Compound" , "Combine into one" , "Merge" .)