The most common and most likely answer to this crossword clue is the 3 plus 4 letter word THE SELF
I've seen this crossword clue in Financial Times
T
H
E
S
E
L
F
More clues leading to the result THE SELF
Buddy explains!
The straight part
We know that "I" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case i = the self.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.