The most common and most likely answer to this crossword clue is the 2 plus 6 letter word IN POCKET
I've seen this crossword clue in The Guardian
I
N
P
O
C
K
E
T
Buddy explains!
The straight part
We know that "when you’ve /made a profit /(2,6)" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case when you’ve /made a profit /(2,6) = in pocket.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.