The most common and most likely answer to this crossword clue is the 6 letter word PROFIT
I've seen this crossword clue in The Daily Telegraph
P
R
O
F
I
T
More clues leading to the result PROFIT
- Academic briefly leading appeal to make money
- Make money if port is drunk
- In favour of healthy gain from trading
- Spin and its advantage
- Favouring appropriate trading success
- Positive result for Formula One team’s head
- Mine admits being in favour of returning earnings
- In favour of appropriate gains
- Tom has healthy advantage
- Gain is mine when rising pro leaves
Buddy explains!

The straight part
We know that "gain" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case gain = profit.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 PROFIT mean?
PROFIT noun- Total income or cash flow minus expenditures. The money or other benefit a non-governmental organization or individual receives in exchange for products and services sold at an advertised price.
- Benefit, positive result obtained.
- In property law, a nonpossessory interest in land whereby a party is entitled to enter the land of another for the purpose of taking the soil or the substance of the soil (coal, oil, minerals, and in some jurisdictions timber and game).
- To benefit (somebody), be of use to (somebody).
- (construed with from) To benefit, gain.
- (construed with from) To take advantage of, exploit, use.