The most common and most likely answer to this crossword clue is the 6 letter word COMMIT
I've seen this crossword clue in The Daily Telegraph
C
O
M
M
I
T
More clues leading to the result COMMIT
Buddy explains!

The straight part
We know that "effect" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case effect = commit.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 COMMIT mean?
COMMIT noun- The act of committing (e.g. a database transaction or source code into a source control repository), making it a permanent change.
- To give in trust; to put into charge or keeping; to entrust; to consign; used with to or formerly unto.
- To put in charge of a jailer; to imprison.
- To have (a person) enter an establishment, such as a hospital or asylum, as a patient.
- To do (something bad); to perpetrate, as a crime, sin, or fault.
- To join a contest; to match; followed by with.
- To pledge or bind; to compromise, expose, or endanger by some decisive act or preliminary step. (Traditionally used only reflexively but now also without oneself etc.)
- To make a set of changes permanent.
- (Latinism) To confound.
- To commit an offence; especially, to fornicate.
- To be committed or perpetrated; to take place; to occur.