The most common and most likely answer to this crossword clue is the 3 letter word OFT
I've seen this crossword clue in The Times
O
F
T
More clues leading to the result OFT
Buddy explains!

The straight part
We know that "That would be ...?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case that would be ...? = oft.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 OFT mean?
OFT adverb- (and in combination) often; frequently; not rarely