25% of tequila drunk around 3rd of April (8)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

Anagram (drunk) of TEQUILA around the third letter of [ap] R [il]. Term used in statistics for one of four divisions of a range of values, so for example the “first quartile” is the lowest 25% of the values. Strictly “quartile” means the actual value at the 25% boundary, but the term is also used to mean the set of values below it.