Cryptic crossword clue
Tortured Pole’s university pal describing resistance as having many uses 3-7

The most common and most likely answer to this crossword clue is the 11 letter word ALL-PURPOSE

I've seen this crossword clue in Financial Times
A
L
L
-
P
U
R
P
O
S
E


Buddy explains!

The straight part
We know that "having many uses" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case having many uses = all-purpose.
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 ALL-PURPOSE mean?

ALL-PURPOSE adjective
  1. For all purposes; general-purpose

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