Want rider sending spades back for port worker (12)
I believe the answer is:
longshoreman
'worker' is the definition.
(longshoreman is a kind of worker)
'want rider sending spades' is the wordplay.
'want' becomes 'long' (longing is a kind of wanting).
'rider sending spades' becomes 'shoreman' (I can't explain this - if you can you should give a lot more credence to this answer).
'long'+'shoreman'='LONGSHOREMAN'
'back for port' 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 longshoreman that I've seen before include "Dock worker" , "Stevedore" , "docker" .)