The most common and most likely answer to this crossword clue is the 7 letter word GUMBOOT
I've seen this crossword clue in The Times
G
U
M
B
O
O
T
Buddy explains!

The straight part
We know that "it's rubbery!" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case it's rubbery! = gumboot.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 GUMBOOT mean?
GUMBOOT noun- A type of boot made of rubber.
- A style of popular music traditionally associated with gold miners.
- Generic black tea.