The most common and most likely answer to this crossword clue is the 1 plus 7 plus 2 plus 4 letter word I THOUGHT AS MUCH
I've seen this crossword clue in Financial Times
I
T
H
O
U
G
H
T
A
S
M
U
C
H
Buddy explains!
The straight part
We know that "that’s no surprise" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case that’s no surprise = i thought as much.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.