The most common and most likely answer to this crossword clue is the 6 letter word AFFECT
I've seen this crossword clue in The Sunday Telegraph
A
F
F
E
C
T
More clues leading to the result AFFECT
- Simulate emotion
- Court after blunder not having good influence
- Pretend to influence
- Impact fellow with iron, in turn
- Influence a fine pink paper that covers the City
- What feckless lack mostly? Stern outside influence
- Influence a paper put round fine city
- Pretend to have influence
- Assume influence
- Strike force vacated France when opening front
Buddy explains!

The straight part
We know that "Impact" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case impact = affect.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 AFFECT mean?
AFFECT verb- To influence or alter.
- To move to emotion.
- Of an illness or condition, to infect or harm (a part of the body).
- To dispose or incline.
- To tend to by affinity or disposition.
- To assign; to appoint.
- To make a show of; to put on a pretense of; to feign; to assume. To make a false display of.
- To aim for, to try to obtain.
- To feel affection for (someone); to like, be fond of.
- To show a fondness for (something); to choose.
- One's mood or inclination; mental state.
- A desire, an appetite.
- A subjective feeling experienced in response to a thought or other stimulus; mood, emotion, especially as demonstrated in external physical signs.