The most common and most likely answer to this crossword clue is the 1 plus 4 plus 2 plus 8 plus 1 plus 2 letter word A LOAD OF COBBLERS - DD
I've seen this crossword clue in The Times
A
L
O
A
D
O
F
C
O
B
B
L
E
R
S
-
D
D
Buddy explains!
The straight part
We know that "Rubbish/description of a bootmakers’ union" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case rubbish/description of a bootmakers’ union = a load of cobblers - dd.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.