The most common and most likely answer to this crossword clue is the 10 letter word CLODHOPPER
I've seen this crossword clue in The Daily Telegraph
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More clues leading to the result CLODHOPPER
- Lout, behold, and daughter boarding helicopter
- Boot finding flea, say, on some ground
- Metal chains hold awfully clumsy boot
- Peasant repaired old axe outside
- Fool old battered helicopter controls
- Axe captivating strange old bumpkin
- Hold out to spike policeman’s shoe
- Boot, one going on one foot: some earth on top
- Caught by policeman, hold criminal peasant
- Learner wearing joke jumper is a clumsy fool
Buddy explains!

The straight part
We know that "lummox" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case lummox = clodhopper.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does CLODHOPPER mean?
CLODHOPPER noun- A strong shoe for heavy-duty use, a boot.
- Any kind of shoe.
- United States Navy ankle length work shoes, distinct from dress shoes or combat boots.
- A peasant or yokel.
- A clumsy or foolish person.
- Wheatear; any of various passerine birds.