Cryptic crossword clue
Old boy with bits of firewood, any number being in particular shapes 7

The most common and most likely answer to this crossword clue is the 7 letter word OBLONGS

I've seen this crossword clue in Financial Times
O
B
L
O
N
G
S

Buddy explains!

The straight part
We know that "particular shapes" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case particular shapes = oblongs.
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 OBLONGS mean?

OBLONGS noun
  1. Something with an oblong shape.
  2. A rectangle having length greater than width or width greater than length.

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