The most common and most likely answer to this crossword clue is the 4 letter word REAL
I've seen this crossword clue in The Times
R
E
A
L
More clues leading to the result REAL
- Some are altogether genuine
- Between right and left, each is genuine
- Genuine old Spanish coin
- Genuine reading not needing citation
- Substantial addition to pure alcohol
- Genuine antique Spanish coin
- Authentic case of egomania in sport
- ‘Sincere’ earl corrupted
- Rehearsal outside – in pairs!
- True part of a film we hear
Buddy explains!

The straight part
We know that "Genuine/old Spanish coin" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case genuine/old spanish coin = real.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 REAL mean?
REAL noun- A commodity; see realty.
- (grammar) One of the three genders that the common gender can be separated into in the Scandinavian languages.
- A real number.
- A realist.
- True, genuine, not merely nominal or apparent.
- Genuine, not artificial, counterfeit, or fake.
- Genuine, unfeigned, sincere.
- Actually being, existing, or occurring; not fictitious or imaginary.
- That has objective, physical existence.
- Having been adjusted to remove the effects of inflation; measured in purchasing power (contrast nominal).
- Relating to the result of the actions of rational agents; relating to neoclassical economic models as opposed to Keynesian models.
- (of a number) Being either a rational number, or the limit of a convergent infinite sequence of rational numbers: being one of a set of numbers with a one-to-one correspondence to the points on a line.
- Relating to immovable tangible property.
- Absolute, complete, utter.
- Signifying meritorious qualities or actions especially as regard the enjoyment of life, prowess at sports, or success wooing potential partners.
- Really, very.
- Former unit of currency of Spain and Spain's colonies.
- A coin worth one real.
- A unit of currency used in Portugal and its colonies from 1430 until 1911, and in Brazil from 1790 until 1942.
- A coin worth one real.
- A unit of currency used in Brazil since 1994. Symbol: R$.
- A coin worth one real.