Worked in a forest and made slow plodding progress? (8)
I believe the answer is:
lumbered
'worked' is the definition.
The answer and definition can be both to do with contact as well as being past participle verbs.
Perhaps you can see a link between them that I don't see?
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for lumbered that I've seen before include "Plodded along" , "Moved clumsily in dumb reel" , "loaded" , "Stuck (with)" , "Burdened with unwanted responsibility" .)