The most common and most likely answer to this crossword clue is the 8 letter word TOWELLED
I've seen this crossword clue in Financial Times
T
O
W
E
L
L
E
D
More clues leading to the result TOWELLED
Buddy explains!

The straight part
We know that "had a rub down" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case had a rub down = towelled.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 TOWELLED mean?
TOWELLED verb- To hit with a towel.
- To dry by using a towel.
- To block up (a door, etc.) with a towel, to conceal the fumes of a recreational drug.
- To beat with a stick.