The most common and most likely answer to this crossword clue is the 2 plus 4 plus 2 letter word SO LONG AS
I've seen this crossword clue in The Times
S
O
L
O
N
G
A
S
More clues leading to the result SO LONG AS
Buddy explains!
The straight part
We know that "If" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case if = so long as.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.