The most common and most likely answer to this crossword clue is the 10 letter word TORRENTIAL
I've seen this crossword clue in Financial Times
T
O
R
R
E
N
T
I
A
L
More clues leading to the result TORRENTIAL
- Heavy trailer not in need of refurbishment
- Referring to fall maybe in hill latrine, messy
- Go off returning hire car carrying one driving
- Note trail winding around river with a rushing stream?
- Like violent 10, changing terrain to lake?
- Teeming rain let loose under storm centre?
- As heavy rain is famous feature of Glastonbury, I learnt swimming
- Heavy rent demanded by upset tailor
- Driving rain let loose below storm’s centre
- Rotten liar’s awful driving
Buddy explains!

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 TORRENTIAL mean?
TORRENTIAL adjective- Coming or characterized by torrents; flowing heavily or in large quantities.