The most common and most likely answer to this crossword clue is the 6 plus 4 letter word STRUCK HOME
I've seen this crossword clue in The Daily Telegraph
S
T
R
U
C
K
H
O
M
E
More clues leading to the result STRUCK HOME
Buddy explains!
The straight part
We know that "was effective" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case was effective = struck home.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.