The most common and most likely answer to this crossword clue is the 5 plus 5 letter word FORCE FEEDS
I've seen this crossword clue in The Guardian
F
O
R
C
E
F
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S
Buddy explains!

The straight part
We know that "Insists on giving vital supplies" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case insists on giving vital supplies = force feeds.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 FORCE FEEDS mean?
FORCE FEEDS verb- To force a person or animal to ingest food, for example by stuffing food down the throat, or using a tube passed into the stomach.
- More broadly, also referring to forcing the drinking of a beverage or other liquid
- To force someone to take in information or accept an ideology.