The most common and most likely answer to this crossword clue is the 3 letter word OXO
I've seen this crossword clue in The Guardian
O
X
O
More clues leading to the result OXO
Buddy explains!
The straight part
We know that "Stock in trade" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case stock in trade = oxo.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 OXO mean?
OXO noun- (in combination) A substituent oxygen atom connected to another atom by a double bond
- The game noughts and crosses