The most common and most likely answer to this crossword clue is the 5 letter word GAYER
G
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More clues leading to the result GAYER
Buddy explains!

The straight part
We know that "more gleeful" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case more gleeful = gayer.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 GAYER mean?
GAYER adjective- (possibly obsolete) Happy, joyful, and lively.
- Quick, fast.
- (possibly obsolete) Festive, bright, or colourful.
- Sexually promiscuous (of any gender), (sometimes particularly) engaged in prostitution.
- Homosexual:
- A pejorative:
- (of a dog's tail) Upright or curved over the back.
- (possibly obsolete) Considerable, great, large in number, size, or degree.
- Somebody who is gay (in the sense of either homosexual or uncool).