The most common and most likely answer to this crossword clue is the 4 letter word PILE
I've seen this crossword clue in The Daily Telegraph
P
I
L
E
More clues leading to the result PILE
- Big house, load of money!
- Nuclear reactor is a singular source of discomfort
- Young animal going round Corsica perhaps in collision
- Fortune pocketed by Disraeli Parliament upheld
- Tart possessing large mansion
- Heap of carpets
- Exercise over the Italian's stack
- Heavy machines Greek character guided over waterways
Buddy explains!

The straight part
We know that "Fortune" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fortune = pile.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 PILE mean?
PILE noun- A mass of things heaped together; a heap.
- A group or list of related items up for consideration, especially in some kind of selection process.
- A mass formed in layers.
- A funeral pile; a pyre.
- A large amount of money.
- A large building, or mass of buildings.
- A bundle of pieces of wrought iron to be worked over into bars or other shapes by rolling or hammering at a welding heat; a fagot.
- A vertical series of alternate disks of two dissimilar metals (especially copper and zinc), laid up with disks of cloth or paper moistened with acid water between them, for producing a current of electricity; a voltaic pile, or galvanic pile.
- An atomic pile; an early form of nuclear reactor.
- The reverse (or tails) of a coin.
- A list or league
- (often used with the preposition "up") To lay or throw into a pile or heap; to heap up; to collect into a mass; to accumulate
- To cover with heaps; or in great abundance; to fill or overfill; to load.
- To add something to a great number.
- (of vehicles) To create a hold-up.
- To place (guns, muskets, etc.) together in threes so that they can stand upright, supporting each other.
- A dart; an arrow.
- The head of an arrow or spear.
- A large stake, or piece of pointed timber, steel etc., driven into the earth or sea-bed for the support of a building, a pier, or other superstructure, or to form a cofferdam, etc.
- One of the ordinaries or subordinaries having the form of a wedge, usually placed palewise, with the broadest end uppermost.
- To drive piles into; to fill with piles; to strengthen with piles.
- (usually in the plural) A hemorrhoid.
- Hair, especially when very fine or short; the fine underfur of certain animals. (Formerly countable, now treated as a collective singular.)
- The raised hairs, loops or strands of a fabric; the nap of a cloth.
- To give a pile to; to make shaggy.