The most common and most likely answer to this crossword clue is the 4 letter word GLAD
I've seen this crossword clue in Financial Times
G
L
A
D
More clues leading to the result GLAD
- Good boy is happy
- Joyful leading lady's part
- Gratified these rags become stylish clothes
- Happy to wander round lake
- Short girl, happy with grand, young man
- What’s youngster after end of fagging?
- Happy to see prime minister losing weight
- & 24ac. Act like campaigning politician with a lot of money – “son needs support”
- Happy clearing last away
- Good boy feeling pleasure
Buddy explains!

The straight part
We know that "Happy" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case happy = glad.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 GLAD mean?
GLAD verb- To make glad
- Pleased, happy, gratified.
- Having a bright or cheerful appearance; expressing or exciting joy; producing gladness.