The most common and most likely answer to this crossword clue is the 8 letter word STICKIER
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Buddy explains!
The straight part
We know that "More tenacious" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case more tenacious = stickier.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 STICKIER mean?
STICKIER adjective- Able or likely to stick.
- Potentially difficult to escape from.
- Of weather, hot and windless and with high humidity, so that people feel sticky from sweating.
- (of a setting) Persistent.
- (of a window) Appearing on all virtual desktops.
- (of threads on a bulletin board) Fixed at the top of the list of topics or threads so as to keep it in view.
- (of a website) Compelling enough to keep visitors from leaving.