The most common and most likely answer to this crossword clue is the 8 letter word APPROVED
I've seen this crossword clue in The Sunday Telegraph
A
P
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R
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More clues leading to the result APPROVED
Buddy explains!

The straight part
We know that "Was happy about" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case was happy about = approved.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 APPROVED mean?
APPROVED verb- To sanction officially; to ratify; to confirm; to set as satisfactory.
- To regard as good; to commend; to be pleased with; to think well of.
- To make proof of; to demonstrate; to prove or show practically.
- (followed by "of") To consider worthy (to); to be pleased (with); to accept.
- To show to be worthy; to demonstrate the merits of.
- (English law) To make profit of; to convert to one's own profit — said especially of waste or common land appropriated by the lord of the manor.
- Having received approval.