The most common and most likely answer to this crossword clue is the 7 letter word TOPPING
I've seen this crossword clue in The Sunday Telegraph
T
O
P
P
I
N
G
More clues leading to the result TOPPING
- First-class food garnish
- First-class relish for food
- . Excellent finishing, not starting
- Wonderful garnish
- Excellent sauce
- Excellent garnish for food
- First-class fare may be enhanced by its addition
- Excellent finishing but not beginning
- Very good thing to have on pizza?
- Dressing, seeing better contact from track and trace
Buddy explains!

The straight part
We know that "First-class/fare may be enhanced by its addition" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case first-class/fare may be enhanced by its addition = topping.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 TOPPING mean?
TOPPING verb- To cover on the top or with a top.
- To cut or remove the top (as of a tree)
- To excel, to surpass, to beat.
- To be in the lead, to be at number one position (of).
- To commit suicide.
- To murder.
- (BDSM) To be the dominant partner in a BDSM relationship or roleplay.
- (gay sexuality) To be the partner who penetrates in anal sex.
- (gay sexuality) To anally penetrate.
- To rise aloft; to be eminent; to tower.
- To predominate.
- To excel; to rise above others.
- To raise one end of (a yard, etc.), making it higher than the other.
- (dyeing) To cover with another dye.
- To put a stiffening piece or back on (a saw blade).
- To arrange (fruit, etc.) with the best on top.
- (of a horse) To strike the top of (an obstacle) with the hind feet while jumping, so as to gain new impetus.
- To improve (domestic animals, especially sheep) by crossing certain individuals or breeds with other superior breeds.
- To cut, break, or otherwise take off the top of (a steel ingot) to remove unsound metal.
- To strike (the ball) above the centre; also, to make (a stroke, etc.) by hitting the ball in this way.
- Any food item added on top of another, such as sprinkles on ice cream or pepperoni on pizza.
- The act of cutting off the top of something.
- The act of raising one extremity of a spar higher than the other.
- Either of the cables that support the ends of a spar or boom.
- The tail of an artificial fly.
- Wonderful
- Assuming superiority; proud.